Feat: add auth provider to users on sign in (#3739)

* feat: merge a new authentication method onto existing user records when emails match

* adds test for invite acceptance and auth provider creation

* addresses comments
- test existing user and invites in different test cases
- update lastActiveAt syncronously when an invite is accepted

* sort arrays in test to prevent nondeterministic test behaivior when doing array compare

server/test/factories.ts

@@ -179,6 +179,7 @@ export async function buildInvite(overrides: Partial<User> = {}) {
     name: `User ${count}`,
     createdAt: new Date("2018-01-01T00:00:00.000Z"),
     invitedById: actor.id,
+    authentications: [],
     ...overrides,
     lastActiveAt: null,
   });