Declare allowExternalMembers on managed groups so deploys stop re-arming the external-member purge (#140)

* Declare allowExternalMembers on managed group settings

Every pulumi up was resetting the Google Workspace per-group setting
ALLOW_EXTERNAL_MEMBERS to false on all managed groups, because the
GroupSettings resources never declared allowExternalMembers and the
provider (SamuZad/googleworkspace 0.11.1) defaults the field to false.
Google then silently purges external-email members from affected groups
roughly 1-2 days after each apply, with no audit events.

Pin the setting to true for all managed groups. External membership
itself remains governed exclusively by config/users.ts entries; this
setting only permits it.

Part of the #133 incident.

* Scope allowExternalMembers per group, derived from membership config

Instead of permitting external members on every managed group, derive
allowExternalMembers per group: true only for groups whose membership
config (config/users.ts) resolves at least one member to a
non-@modelcontextprotocol.io email. Email resolution is factored into
resolveGoogleMemberEmail and shared with GroupMember creation so the
two cannot drift. The field stays declared on every group because the
provider defaults it to false on each apply, after which Google
silently purges external members (#133 incident).

With current config, exactly these groups derive true: maintainers,
registry-wg, antitrust, catch-all. A config test pins this set so
changes to it are always deliberate.

* Make allowExternalMembers an explicit per-role opt-in with config validation

Replace the derived per-group allowExternalMembers (computed from
membership config) with an explicit opt-in: group owners set
allowExternalMembers: true on the role's google config in
src/config/roles.ts, and src/google.ts passes it straight through to
GroupSettings (defaulting to false). The field stays declared on every
group because the provider resets an omitted field to false on each
apply, after which Google silently purges external members (#133).

Roles opting in, matching current membership: maintainers,
registry-maintainers (registry-wg), antitrust, catch-all.

A validate-config check replaces the old pinned-set test: it fails with
an actionable error whenever a group has a member resolving to a
non-@modelcontextprotocol.io email but its role does not opt in, naming
the group, the member email, and the exact config line to add.

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

---------

Co-authored-by: Claude <noreply@anthropic.com>

src/config/roles.ts

@@ -28,6 +28,13 @@ export interface GoogleConfig {
   isEmailGroup?: boolean;
   /** If true, members of this role get a Google Workspace user account */
   provisionUser?: boolean;
+  /**
+   * Opt-in for groups that intentionally include non-@modelcontextprotocol.io
+   * members. Defaults to false. Must stay declared on the GroupSettings
+   * resource: the provider resets an omitted field to false on every apply,
+   * after which Google silently purges external members (#133 incident).
+   */
+  allowExternalMembers?: boolean;
 }
 
 /**
@@ -105,7 +112,7 @@ export const ROLES: readonly Role[] = [
     discord: { role: 'maintainers (synced)' },
     // GWS user accounts are opt-in: maintainers add firstName/lastName/googleEmailPrefix
     // to their entry in users.ts via PR to get an @modelcontextprotocol.io account
-    google: { group: 'maintainers', provisionUser: true },
+    google: { group: 'maintainers', provisionUser: true, allowExternalMembers: true },
   },
   {
     id: ROLE_IDS.DOCS_MAINTAINERS,
@@ -136,7 +143,7 @@ export const ROLES: readonly Role[] = [
     description: 'Official registry builders and maintainers',
     github: { team: 'registry-wg', parent: ROLE_IDS.WORKING_GROUPS },
     discord: { role: 'registry maintainers (synced)' },
-    google: { group: 'registry-wg', provisionUser: true },
+    google: { group: 'registry-wg', provisionUser: true, allowExternalMembers: true },
   },
   {
     id: ROLE_IDS.REGISTRY_COLLABORATORS,
@@ -394,7 +401,7 @@ export const ROLES: readonly Role[] = [
   {
     id: ROLE_IDS.ANTITRUST,
     description: 'Antitrust compliance contacts',
-    google: { group: 'antitrust', isEmailGroup: true },
+    google: { group: 'antitrust', isEmailGroup: true, allowExternalMembers: true },
     // Google only
   },
   {
@@ -406,7 +413,7 @@ export const ROLES: readonly Role[] = [
   {
     id: ROLE_IDS.CATCH_ALL,
     description: 'Catch-all email group',
-    google: { group: 'catch-all', isEmailGroup: true },
+    google: { group: 'catch-all', isEmailGroup: true, allowExternalMembers: true },
     // Google only
   },
 ] as const;

src/config/utils.ts

@@ -27,6 +27,19 @@ export interface Member {
   skipGoogleUserProvisioning?: boolean;
 }
 
+/**
+ * Resolve the email a member joins Google groups with.
+ * Prefers the provisioned GWS email over the personal email. This is the
+ * single source of truth for group-membership emails — src/google.ts uses it
+ * to create memberships, and scripts/validate-config.ts uses it to check that
+ * external members only appear in roles that opt into allowExternalMembers.
+ */
+export function resolveGoogleMemberEmail(member: Member): string | undefined {
+  return member.googleEmailPrefix
+    ? `${member.googleEmailPrefix}@modelcontextprotocol.io`
+    : member.email;
+}
+
 /**
  * Sort roles by GitHub parent dependency (topological sort).
  * Ensures parent teams are created before child teams.