fix: make team_members→auth migration boot reliably (#16)

The deployed migration crash-looped PocketBase (502 on every /api call)
for two reasons, both verified against a production-like DB locally:

1. team_members is referenced by relation fields (team_member_id) in
   micro_learning_completions and theme_session_completions, so
   app.delete(team_members) was blocked — and the swallowed error left
   the create to fail with "Collection name must be unique". Fix: before
   dropping team_members, convert those relation fields to plain text
   (consistent with how user_id is stored elsewhere) and rebuild the
   theme_session_completions unique index on the text column.

2. An enabled OAuth2 provider with empty clientId/clientSecret fails
   validation and aborts the migration. Fix: attach the OIDC provider
   only when ENTRA_CLIENT_ID and ENTRA_CLIENT_SECRET are present;
   otherwise create the auth collection without a provider.

Verified locally with the muchobien/pocketbase image: boots clean both
without Entra env (provider-less) and with env (auth-methods returns the
Microsoft OIDC provider).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

pb_migrations/1781000000_team_members_to_auth.js

@@ -19,7 +19,42 @@
 // re-configure the provider from the PocketBase admin UI (Settings → Auth
 // providers) or ship a follow-up migration.
 migrate((app) => {
-  // 1. Drop the old PIN-based collection (takes the PIN records with it).
+  // 1. Detach relation fields that point at team_members. PocketBase refuses to
+  //    delete a collection that other collections relate to, so before we can
+  //    drop the old PIN-based team_members we convert those relations into plain
+  //    text fields (the id is stored as text — consistent with how user_id is
+  //    stored in test_results / on_demand_attempts). Per-user progress is reset
+  //    anyway, so dropping the FK constraint here is acceptable.
+  const deps = [
+    { name: "micro_learning_completions", relId: "rel_team_member_id",  textId: "txt_mlc_team_member" },
+    { name: "theme_session_completions",  relId: "rel_tsc_team_member", textId: "txt_tsc_team_member" },
+  ];
+  for (const dep of deps) {
+    let c;
+    try { c = app.findCollectionByNameOrId(dep.name); } catch (_) { continue; }
+    // Drop any index that references the team_member_id column.
+    c.indexes = (c.indexes || []).filter((idx) => idx.indexOf("team_member_id") === -1);
+    // Replace the relation field with a text field of the same name.
+    c.fields.removeById(dep.relId);
+    c.fields.add(new Field({
+      type: "text",
+      id: dep.textId,
+      name: "team_member_id",
+      required: false,
+      min: 0,
+      max: 0,
+    }));
+    app.save(c);
+  }
+
+  // Recreate the unique (team_member_id, session_week) guard on the text column.
+  try {
+    const tsc = app.findCollectionByNameOrId("theme_session_completions");
+    tsc.indexes.push("CREATE UNIQUE INDEX `idx_theme_session_completions_user_week` ON `theme_session_completions` (`team_member_id`, `session_week`)");
+    app.save(tsc);
+  } catch (_) { /* collection missing — skip */ }
+
+  // 2. Drop the old PIN-based team_members (now unreferenced).
   try {
     const old = app.findCollectionByNameOrId("team_members");
     app.delete(old);
@@ -28,6 +63,28 @@ migrate((app) => {
   }
 
   const tenant = $os.getenv("ENTRA_TENANT_ID") || "common";
+  const clientId = $os.getenv("ENTRA_CLIENT_ID");
+  const clientSecret = $os.getenv("ENTRA_CLIENT_SECRET");
+
+  // Only configure the OIDC provider when credentials are actually present.
+  // PocketBase rejects an enabled OAuth2 provider with an empty clientId /
+  // clientSecret, which would abort this migration and prevent PocketBase from
+  // starting at all (502 on every /api call). When the secrets are absent the
+  // collection is created without a provider; once the ENTRA_* secrets are set,
+  // configure the provider via the PocketBase admin UI
+  // (Settings → Auth providers → OIDC) or re-apply this migration.
+  const oidcProviders = (clientId && clientSecret) ? [
+    {
+      name: "oidc",
+      clientId: clientId,
+      clientSecret: clientSecret,
+      authURL:     "https://login.microsoftonline.com/" + tenant + "/oauth2/v2.0/authorize",
+      tokenURL:    "https://login.microsoftonline.com/" + tenant + "/oauth2/v2.0/token",
+      userInfoURL: "https://graph.microsoft.com/oidc/userinfo",
+      displayName: "Microsoft",
+      pkce: true,
+    },
+  ] : [];
 
   // 2. Recreate `team_members` as an auth collection (same name → all existing
   //    `user_id` references in test_results, on_demand_attempts,
@@ -56,7 +113,7 @@ migrate((app) => {
     mfa:          { enabled: false, duration: 600, rule: "" },
 
     oauth2: {
-      enabled: true,
+      enabled: oidcProviders.length > 0,
       // Map the OIDC userinfo claims onto our fields.
       mappedFields: {
         id: "",
@@ -64,18 +121,7 @@ migrate((app) => {
         username: "",
         avatarURL: "",
       },
-      providers: [
-        {
-          name: "oidc",
-          clientId:     $os.getenv("ENTRA_CLIENT_ID"),
-          clientSecret: $os.getenv("ENTRA_CLIENT_SECRET"),
-          authURL:     "https://login.microsoftonline.com/" + tenant + "/oauth2/v2.0/authorize",
-          tokenURL:    "https://login.microsoftonline.com/" + tenant + "/oauth2/v2.0/token",
-          userInfoURL: "https://graph.microsoft.com/oidc/userinfo",
-          displayName: "Microsoft",
-          pkce: true,
-        },
-      ],
+      providers: oidcProviders,
     },
 
     fields: [