0.11.0 - 2026-09-06

PR #31, PR #32, plus the post-merge review of #32. Full findings in
dev_docs/pull_requests/2026/31-set-default-currency-repromote/CLAUDE_REVIEW.md
and dev_docs/pull_requests/2026/32-currency-e1-display-currency-cache/CLAUDE_REVIEW.md.

Added

• Request-scoped display currency. Currency.put_request_currency/1 /
  get_request_currency/0 let a host set, per request, the currency a
  shopper should see and be charged in, independent of the shop's base
  currency. get_base_currency/0 (cached), get_display_currency/0 and
  resolve_display_currency/1 resolve it with a fail-safe: an unknown,
  disabled, or non-positive-rate code falls back to the base currency and
  logs once per process per offending code, rather than crashing or showing
  a broken price.
• Currency.present/3 — the one place a base-currency amount becomes a
  display-currency amount. Resolves the base and target fresh on every call
  (a rate edit is visible on the next call), or, with opts[:rate], uses a
  caller's own frozen rate (a cart's or order's snapshot) without
  re-checking the target's live usability — a frozen rate must survive the
  target being disabled after the freeze.
• Currency.effective_rate/2 — the base -> target multiplier a cart
  freezes at creation, rounded to six decimal places.
• Currency-table caching (§13). get_base_currency/0 and
  get_currency_by_code/1 are backed by a PhoenixKit.Cache instance
  (5 minute TTL), invalidated wholesale by every currency writer. Cuts
  Currency.present/3's per-call query cost from 3 to ~0 once warm — a
  catalog page converting dozens of prices no longer pays for it per price.
• Migration chain V3 — adds phoenix_kit_orders.base_currency,
  .exchange_rate and .base_total (nullable, no backfill), the columns
  PhoenixKitBilling.Order now declares for a later stage's frozen order
  pricing. Added post-merge: PR #32 shipped the schema fields on the
  assumption that a core release would add these columns, but the core
  release in question had not been published, so every Order query broke
  on the currently published core. This chain now adds them itself, using
  the same names/types that core release will use, so its own
  ADD COLUMN IF NOT EXISTS and backfill still work unchanged once it ships.

Changed

• billing_default_currency is no longer read. Every internal reader
  (order/subscription creation, dashboard stats, the order form) now uses
  the is_default row of phoenix_kit_currencies via get_base_currency/0.
  The dead "Default Currency" select on the settings page (it wrote a
  setting nothing read) is removed along with it.

Fixed

• set_default_currency/1: re-promoting the currency that is already
  default no longer clears is_default entirely. The base-rate
  renormalization added in 0.10.0 demoted the target's own row in the
  database while the caller's in-memory struct still read is_default: true, so Ecto's changeset diff saw no change and never re-promoted it.
  The function now reloads the row before both the guard check and the
  promoting changeset, and forces :is_default/:exchange_rate into the
  changeset regardless of what the reload reports.