feat(nut04/05)!: quote accounting and custom payment method base structs

[robwoodgate]

Summary

Matures the NUT-04/05 base payloads so wallets can handle generic and custom payment methods, implementing:

• Align NUT-04 mint quote accounting with amount_paid / amount_issued nuts#377 — mint quote accounting: amount_paid, amount_issued and updated_at become base mint quote response fields for every payment method; state is deprecated (but always populated for bolt11).

• custom payment methods nuts#382 — custom payment methods: base request/response structs widened per the shapes suggested in review, generic quote responses get base normalization + validation, and new MintQuoteGenericResponse / MeltQuoteGenericResponse passthrough types are the defaults on the generic quote methods so custom-method fields are reachable without casting.

• add method field to quote responses, closes #378 nuts#387 — every quote response carries a method field: populated from the request endpoint when the mint omits it (no mint ships it yet), throwing when a reported method disagrees with the endpoint. Once mints implement it, NUT-17 generic mint_quote/melt_quote notifications become routable by method.

Follows up on #672 (nuts#374 method_name), which already merged.

Design notes

• Required-but-derived accounting. For mints that predate quote accounting, amount_paid/amount_issued are derived from the legacy single-use state + amount (UNPAID → 0/0, PAID → amount/0, ISSUED → amount/amount); conversely a missing bolt11 state is derived from the accounting fields. Underivable responses throw, matching the existing melt-side strictness. updated_at is number | null (null when the mint does not report it — it cannot be derived).
• Base shapes per the nuts#382 review suggestions. Mint quote request base gains optional amount/description; expiry moves into the mint quote response base (normalized to null when unset); melt quote request base gains optional amount; melt quote response base gains required request and optional fee_reserve (bolt methods keep it required, onchain keeps fee_options).
• Mintable amount enforced for all methods. validateMintQuoteAvailableAmount loses its bolt12/onchain gate: mintable = amount_paid − amount_issued is checked whenever the quote object carries accounting fields. Stored quotes without them (pre-accounting) skip the check, as before.
• Method-id validation (^[a-z0-9_-]+$) and the generic /v1/{mint,melt}/quote/{method} plumbing already existed and are unchanged.

Breaking changes

• MintQuoteBaseResponse requires amount_paid, amount_issued, updated_at, expiry; MeltQuoteBaseResponse requires request. Type-breaking for code constructing quote literals; runtime consumers are unaffected because normalization guarantees the fields.
• Non-conformant quote responses that previously passed through unvalidated (mint quotes missing quote/request/unit or underivable accounting; melt quotes missing request) now throw Invalid response from mint.

Sequencing

Suggest merging in order:#675 → this.

Test plan

• New unit tests: state↔accounting derivation matrix, updated_at/expiry normalization, custom-method base validation (mint + melt), unknown-field passthrough, generalized available-amount enforcement.
• 1605 node tests pass; tsc clean; api report regenerated.

[codecov]

Codecov Report

❌ Patch coverage is 95.45455% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 92.36%. Comparing base (f568ed3) to head (85b1b53).
⚠️ Report is 1 commits behind head on main.
✅ All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
src/mint/Mint.ts	95.23%	1 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #698      +/-   ##
==========================================
- Coverage   92.40%   92.36%   -0.04%     
==========================================
  Files          54       54              
  Lines        4990     5018      +28     
  Branches     1224     1237      +13     
==========================================
+ Hits         4611     4635      +24     
- Misses        160      163       +3     
- Partials      219      220       +1     

Flag	Coverage Δ
integration	38.87% <45.45%> (+0.20%)	⬆️

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