fix(firestore-send-email): preparePayload fix

[cabljac]

This PR is to actually fix #2419

We extract preparePayload into a dependency injection pattern, and cover it with unit tests, and ensure template/message merging is being done correctly

[Copilot]

Pull Request Overview

This PR refactors payload preparation for sending emails by extracting the preparePayload logic into its own module using dependency injection and enhancing its unit tests.

• Introduces a new preparePayload module with dependency injection support.
• Removes the inline preparePayload implementation from index.ts.
• Adds comprehensive unit tests covering various payload scenarios.

Reviewed Changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
firestore-send-email/functions/src/prepare-payload.ts	New module for payload preparation with dependency injection and template merging.
firestore-send-email/functions/src/index.ts	Removal of inline preparePayload; added dependency injection initialization.
firestore-send-email/functions/tests/validation.test.ts	Added a test case for payload validation when no message object is provided.
firestore-send-email/functions/tests/prepare-payload.test.ts	New tests to cover multiple scenarios for template and message merging in payloads.
firestore-send-email/CHANGELOG.md	Changelog update with a fix entry for payload validation.

Comments suppressed due to low confidence (1)

firestore-send-email/functions/src/prepare-payload.ts:6

• Consider using more specific types instead of 'any' for 'db' to improve type safety and enable better IntelliSense.

let db: any;

[Copilot]

Pull Request Overview

This PR refactors the payload preparation logic into a dedicated module with dependency injection, enhances validation for attachments, and updates test and CI configurations to improve coverage.

• Extract preparePayload into prepare-payload.ts and wire it via setDependencies
• Add Zod schemas for attachments and adjust message schema to allow nullable text/html
• Update tests to cover attachment validation and add coverage tooling

Reviewed Changes

Copilot reviewed 9 out of 9 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
functions/src/validation.ts	Added attachmentSchema and attachmentsSchema, updated baseMessageSchema to allow nullable content
functions/src/prepare-payload.ts	New module: DI for Firestore and template engine, unified payload validation and merging logic
functions/src/index.ts	Removed inline preparePayload, now imports and configures it via setDependencies
functions/package.json	Added coverage and SendGrid E2E test scripts
functions/jest.config.js	Configured coverage collection and reporting
functions/tests/validation.test.ts	Added unit tests for various attachment scenarios
functions/tests/e2e/sendgrid.test.ts	New E2E tests for SendGrid integration
CHANGELOG.md	Updated to version 0.2.2 with validation fix entry

Comments suppressed due to low confidence (1)

firestore-send-email/functions/src/prepare-payload.ts:29

• The new preparePayload module encapsulates key logic (template merging and UID-to-email resolution) but lacks dedicated unit tests. Add tests for payload merging, attachment handling, and UID lookup behavior to ensure this logic stays correct.

export async function preparePayload(

[CorieW]

Lgtm