dashboard: a Slipstream page, and withdrawing a slipstream tx from admin

[rsantacroce]

What

This is the dashboard half of slipstream, stacked on #83. Its base is feat/slipstream-service, so the diff here is only the dashboard. It retargets to main once #83 merges.

• Public /slipstream is shown in the nav only when SLIPSTREAM_API_URL is set. It has four parts:
  • Fees: the minimum submission rate, the current mineable rate, what is required now, and how recently that was read from the template.
  • Submit: a curl line pointing at PUBLIC_SLIPSTREAM_URL, and a link to the pool's info.json.
  • Recent transactions: each with its fee rate and status.
    • Statuses: in template, mined, confirmed, or dropped/expired with a reason.
    • The block is shown with (ours) or (another pool).
• Admin → Tools lists the txs that are still open, each with a Withdraw button (CSRF-gated like every admin action).
  • Withdrawing calls removeslipstreamtx on the enforcer (ENFORCER_GBT_URL), because the enforcer is what holds the txs.
  • On its next poll the service records the tx as dropped (withdrawn).
  • Without ENFORCER_GBT_URL the list still shows, but the buttons do not.

Design notes

• The page reads the slipstream service's API, not slipstream.db. The service stays the only owner of its schema, and there is no second reader to keep in step.
• If the service is down, the page says so. It costs the page one card, not the page, and the rest of the dashboard is unaffected.
• Withdraw goes to the enforcer, not the service. The service has no authenticated surface to take it from, and the dashboard's admin auth already guards this route.

Testing

• dashboard/test/slipstream.test.js (6 new tests):
  • The page renders both rates, the submit line, statuses and reasons.
  • It degrades when the service is down.
  • The nav link appears only when slipstream is enabled.
  • Admin tools lists open txs with withdraw forms.
  • fetchSlipstream works against a stub service.
  • Withdraw sends removeslipstreamtx to a stub enforcer.
• The full dashboard suite passes: 195 tests.
• Live, against a real stack: patched bitcoind (regtest), the enforcer from feat: accept slipstream txs on the block template server bip300301_enforcer#642 with --enable-slipstream, the slipstream service, and this dashboard.
  • A submitted non-standard tx was mined and confirmed. The page showed it as confirmed at its block height.
  • A second tx was withdrawn from Admin → Tools. The flash said withdrew 1 tx(s), the service recorded accepted, in_template, dropped (withdrawn), and the page showed it as dropped.

Found, not fixed here

Without a shares.db (a proxy that has never run), / returns 500 from views/index.ejs:71. This is the same on the base branch, so it is not from this change.