Authenticate against any OIDC provider, for on-premises installs

The seam existed with only a Supabase implementation, so an on-prem deployment
had no way to authenticate. A customer running PIG inside their own network
already has Okta, Entra, Keycloak, Auth0 or Google Workspace; asking them to
stand up a second identity system is a serious adoption tax and in a regulated
environment usually refused outright.

Setting PIG_OIDC_ISSUER is normally the whole configuration — the JWKS is
discovered from the issuer's well-known document. PIG_OIDC_JWKS_URI skips
discovery entirely for an air-gapped network. OIDC takes precedence over
Supabase so an on-prem install can leave the hosted values in its environment
file without them quietly taking over.

Three decisions worth stating:

Discovery is resolved lazily and the FAILURE is not cached. Doing it per
request would put the customer's identity provider on the critical path of
every API call; doing it eagerly at boot would mean their IdP rebooting takes
the CRM down with it. So it happens on first use and retries on the next
request.

The audience check is optional but warned about loudly. Without it, a token the
provider issued for ANY other application in the same tenant verifies here — a
token minted for an unrelated internal tool would be accepted as a PIG session.
It cannot be mandatory because some providers legitimately issue
single-audience tokens.

Email falls back through email, preferred_username and upn, because providers
disagree, but a preferred_username without an "@" is ignored — PIG keys
membership on the address, and a bare username must never become an account
identity.

Also fixed a warning that claimed "authentication is DISABLED" on a correctly
configured OIDC deployment. That is worse than silence: an operator who reads
it on a secure install learns to ignore the warnings. The dev bypass itself was
already correct — it keys on the resolved provider rather than on Supabase.

18 new tests, most of them about what the provider must REFUSE: a foreign
signing key, a foreign issuer, a token for a different application, an expired
token, a token with no subject, and a discovery outage that must not become
permanent. Keys are generated per test and the JWKS is served locally, so they
run offline.

Verified: production refuses to start with neither provider, starts with OIDC
alone, enforces 401 on an unauthenticated request, and warns only about the
genuinely missing admin list.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

apps/api/src/lib/config.ts

@@ -33,6 +33,21 @@ const schema = z.object({
   DATABASE_URL: z.string().min(1, 'DATABASE_URL is required.'),
 
   SUPABASE_URL: z.string().url().optional(),
+
+  /*
+   * OIDC — the on-premises path.
+   *
+   * A customer running PIG inside their own network already has an identity
+   * provider. Setting PIG_OIDC_ISSUER switches authentication to it and takes
+   * precedence over any Supabase values left in the environment file.
+   */
+  PIG_OIDC_ISSUER: z.string().url().optional(),
+  /** Optional. Discovered from the issuer when omitted. */
+  PIG_OIDC_JWKS_URI: z.string().url().optional(),
+  /** Strongly recommended — see the boot warning. */
+  PIG_OIDC_AUDIENCE: z.string().optional(),
+  /** Comma-separated, in preference order. Defaults cover most providers. */
+  PIG_OIDC_EMAIL_CLAIMS: z.string().optional(),
   SUPABASE_ANON_KEY: z.string().optional(),
   SUPABASE_SERVICE_KEY: z.string().optional(),
 
@@ -203,17 +218,48 @@ function warnOnFootguns(config: Config): void {
     warn('PIG_ADMIN_EMAILS is empty — no user will have platform-admin rights.');
   }
 
-  if (!config.SUPABASE_URL) {
+  // Keyed on BOTH providers, not just Supabase. An OIDC deployment has
+  // authentication and this warning previously claimed it did not — which is
+  // worse than saying nothing, because an operator reading "authentication is
+  // DISABLED" on a correctly secured install learns to ignore the warnings.
+  if (!config.SUPABASE_URL && !config.PIG_OIDC_ISSUER) {
     warn(
-      'SUPABASE_URL is not set — authentication is DISABLED and every request ' +
-        'runs as the development user. Never do this in production.',
+      'No identity provider is configured (SUPABASE_URL or PIG_OIDC_ISSUER) — ' +
+        'authentication is DISABLED and every request runs as the development ' +
+        'user. Never do this in production.',
     );
   }
 
-  if (config.isProduction && !config.SUPABASE_URL) {
+  if (config.PIG_OIDC_ISSUER && config.SUPABASE_URL) {
+    warn(
+      'Both PIG_OIDC_ISSUER and SUPABASE_URL are set — OIDC takes precedence and ' +
+        'Supabase will not be used for authentication.',
+    );
+  }
+
+  if (config.PIG_OIDC_ISSUER && !config.PIG_OIDC_AUDIENCE) {
+    // Not fatal, because some providers issue single-audience tokens where it
+    // adds nothing — but on a shared corporate tenant this is the difference
+    // between "a token for PIG" and "a token for anything in the company".
+    warn(
+      'PIG_OIDC_AUDIENCE is not set. Any token your identity provider issued for ' +
+        'ANY application in the same tenant will be accepted here. Set it unless ' +
+        'you are certain that is safe.',
+    );
+  }
+
+  if (config.PIG_OIDC_ISSUER && config.SUPABASE_SERVICE_KEY) {
+    warn(
+      'SUPABASE_SERVICE_KEY is set while running on OIDC. Self-registration mints ' +
+        'Supabase accounts, which an OIDC deployment does not use — unset it and ' +
+        'provision users through your identity provider instead.',
+    );
+  }
+
+  if (config.isProduction && !config.SUPABASE_URL && !config.PIG_OIDC_ISSUER) {
     throw new Error(
-      'Refusing to start: NODE_ENV=production with no SUPABASE_URL would serve ' +
-        'the entire CRM unauthenticated.',
+      'Refusing to start: NODE_ENV=production with neither SUPABASE_URL nor ' +
+        'PIG_OIDC_ISSUER would serve the entire CRM unauthenticated.',
     );
   }