Add a generic tax ID formatter

[methodofaction]

Why

Tax IDs were rendered as a bare code with the country in parentheses — NIF: (ES) B98602642 — with one hardcoded exception for Germany, whose USt-IdNr. is only valid with the DE prefix.

Germany is not alone. In AT, CH, DE, FR, IE, NL, NO and SE the country code is genuinely part of the national identifier. GOBL strips it on normalization (tax.NormalizeIdentity trims the country prefix, since the country lives in tax_id.country), so it has to be put back when presenting the identity. Separately, for most EU regimes the prefix belongs to the intra-community VAT identification number rather than the domestic one — art. 226(3)(4) of the VAT Directive requires both parties' VAT identification numbers on a cross-border supply, and those always carry the prefix.

What changed

New components/taxid package. One table of country rules replaces the German special case:

var rules = map[l10n.TaxCountryCode]rule{
	l10n.AT.Tax(): {prefixed: true},
	l10n.CH.Tax(): {prefixed: true, format: formatCH},
	l10n.CO.Tax(): {format: formatCO},
	...
}

Format(ctx, tID) returns Formatted{Label, Code, Country}, where an empty Country means the prefix belongs inside the code. Three cases:

1. Prefix is part of the national identifier — AT, CH, DE, FR, IE, NL, NO, SE. Always joined.
2. Intra-community — supplier and customer in two different EU member states, checked against the issue date via Identity.InEU. The identity itself is EU-checked too, so a non-EU third party on an intra-EU invoice keeps its national form.
3. Otherwise — the national form, country in parentheses as before.

Local layouts live alongside: CO (901.585.284-3), CH (CHE-123.456.789), NO (NO 123456785 MVA).

Document in the rendering context. org.Party only ever receives a party, so the intra-community check had nothing to work with. Added internal.WithDocument / internal.DocumentFrom, set once in Render. It degrades to the national form when absent, so org.Party rendered standalone still works.

Labels are now translatable. Identifier names moved out of Go into org.party.labels in the locales, keyed by lowercased tax country code and falling back to the existing default:

labels:
  default: "TIN"
  ar: "CUIT"
  de: "USt-IdNr."
  ...

Keys are absolute rather than scope-relative, so they resolve wherever a tax identity is rendered.

Call sites. party.templ loses the taxIDLabel / taxIDCode / taxIDCodeIncludesCountry trio for a single taxid.Format call. The "on behalf of" line seller in lines.templ now uses the same formatter instead of printing a bare code.

Output changes

Only four distinct lines moved across the whole example set:

- NIF: (ES) B98602642      + NIF: ESB98602642        (ES→NL, intra-community)
- TIN: (NL) 000099995B57   + TIN: NL000099995B57
- TVA: (FR) 44732829320    + TVA: FR44732829320      (FR prefix is integral)
- TVA: (FR) 39356000000    + TVA: FR39356000000

examples/out is regenerated.

For the reviewer

• Breaking: co.FormatTaxIDCode was removed from components/regimes/co. It was only used by party.templ; the logic now lives in components/taxid next to the Swiss and Norwegian layouts.
• Only English labels are populated. Every other locale inherits them via LoadWithDefault(…, "en"), so nothing regressed, but GST Reg No. is English prose and a native speaker should decide its form in the other languages. Those are one-line additions per locale.
• Judgement calls worth a second opinion: the prefixed set follows the "prefix is genuinely part of the national identifier" list, which puts NO in and leaves GB and GR/EL out — GB VAT numbers are often written GB… in practice even though it is not required. I also did not add digit grouping beyond CO, CH and NO.

Tests

New components/taxid/taxid_test.go covers each country rule, the nil identity, the domestic / intra-EU / export / non-EU-third-party paths, and label localization (a country with no name of its own picks up the locale's generic label; a named country keeps its name across languages). go test ./... passes.

🤖 Generated with Claude Code

[Copilot]

Pull request overview

This PR introduces a centralized, rule-driven formatter for tax identities so rendered documents can present Tax IDs in the correct national or intra-community (EU cross-border) form, replacing the previous one-off Germany special case and per-template formatting logic.

Changes:

• Added a new components/taxid package that formats tax identities (including country-prefix rules and a few country-specific layouts) and returns structured output for templates.
• Propagated the rendered document through context.Context (internal.WithDocument / DocumentFrom) so components like org.Party can decide whether intra-community VAT formatting applies.
• Moved Tax ID labels into locales (org.party.labels.*) and updated template call sites to use taxid.Format, regenerating examples/out.

Reviewed changes

Copilot reviewed 8 out of 22 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
locales/en/app.yml	Adds translatable tax-identity labels keyed by tax country code under org.party.labels.*.
internal/document.go	Adds WithDocument / DocumentFrom context helpers to expose the current document to sub-components.
goblhtml.go	Stores the extracted document in the rendering context for downstream formatting decisions.
components/taxid/taxid.go	Implements rule-based Tax ID formatting (prefix rules, intra-community detection, and country-specific layouts).
components/taxid/taxid_test.go	Adds unit tests covering formatting rules, intra-community behavior, nil handling, and label localization.
components/regimes/co/co.go	Removes Colombia-specific Tax ID formatter (logic moved into components/taxid).
components/org/party.templ	Replaces ad-hoc Tax ID label/code logic with a single taxid.Format call.
components/org/party_templ.go	Regenerated templ output reflecting the updated Tax ID formatting logic.
components/bill/lines.templ	Updates “on behalf of” seller line to use taxid.Format(...).Code instead of raw code.
components/bill/lines_templ.go	Regenerated templ output reflecting the updated seller Tax ID formatting.
examples/out/invoice-es-reverse-charge.html	Regenerated output reflecting intra-community VAT prefix formatting changes.
examples/out/fr-self-billed-invoice.html	Regenerated output reflecting FR prefix-as-integral formatting.
examples/out/fr-invoice.html	Regenerated output reflecting FR prefix-as-integral formatting.
examples/out/fr-invoice-units.fr.html	Regenerated output reflecting FR prefix-as-integral formatting.
examples/out/fr-invoice-delivery.html	Regenerated output reflecting FR prefix-as-integral formatting.
examples/out/fr-facturx-invoice.html	Regenerated output reflecting FR prefix-as-integral formatting.
examples/out/fr-ctc-invoice-b2bint.html	Regenerated output reflecting FR prefix-as-integral formatting.
examples/out/fr-ctc-invoice-b2b.html	Regenerated output reflecting FR prefix-as-integral formatting.
examples/out/fr-ctc-invoice-advance.html	Regenerated output reflecting FR prefix-as-integral formatting.
examples/out/fr-ctc-credit-note.html	Regenerated output reflecting FR prefix-as-integral formatting.
examples/out/fr-choruspro-invoice.html	Regenerated output reflecting FR prefix-as-integral formatting.
examples/out/de-choruspro-invoice.html	Regenerated output reflecting FR prefix-as-integral formatting in DE example set.

Files not reviewed (2)

• components/bill/lines_templ.go: Generated file
• components/org/party_templ.go: Generated file

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[pedrorfdez]

LGTM