(core) Remove LoginSession, which was mainly serving situations that are no longer used.

Summary:
In the past, Cognito sign-ins were intended to give authorization to some AWS
services (like SQS); various tokens were stored in the session for this
purpose. This is no longer used. Profiles from Cognito now serve a limited
purpose: first-time initialization of name and picture, and keeping track of
which login method was used. For these remaining needs, ScopedSession is
sufficient.

Test Plan:
Existing test pass. Tested manually that logins work with Google and
Email + Password. Tested manually that on a clean database, name and picture
are picked up from a Google Login.

Reviewers: paulfitz

Reviewed By: paulfitz

Differential Revision: https://phab.getgrist.com/D2907

app/server/lib/BrowserSession.ts

@@ -8,19 +8,19 @@ export interface SessionUserObj {
   // a grist-internal identify for the user, if known.
   userId?: number;
 
-  // The user profile object. When updated, all clients get a message with the update.
+  // The user profile object.
   profile?: UserProfile;
 
-  // Authentication provider string indicating the login method used.
+  // [UNUSED] Authentication provider string indicating the login method used.
   authProvider?: string;
 
-  // Login ID token used to access AWS services.
+  // [UNUSED] Login ID token used to access AWS services.
   idToken?: string;
 
-  // Login access token used to access other AWS services.
+  // [UNUSED] Login access token used to access other AWS services.
   accessToken?: string;
 
-  // Login refresh token used to retrieve new ID and access tokens.
+  // [UNUSED] Login refresh token used to retrieve new ID and access tokens.
   refreshToken?: string;
 }
 
@@ -133,6 +133,26 @@ export class ScopedSession {
     return getSessionUser(session, this._org, this._userSelector) || {};
   }
 
+  // Retrieves the user profile from the session.
+  public async getSessionProfile(prev?: SessionObj): Promise<UserProfile|null> {
+    return (await this.getScopedSession(prev)).profile || null;
+  }
+
+  // Updates a user profile. The session may have multiple profiles associated with different
+  // email addresses. This will update the one with a matching email address, or add a new one.
+  // This is mainly used to know which emails are logged in in this session; fields like name and
+  // picture URL come from the database instead.
+  public async updateUserProfile(profile: UserProfile|null): Promise<void> {
+    if (profile) {
+      await this.operateOnScopedSession(async user => {
+        user.profile = profile;
+        return user;
+      });
+    } else {
+      await this.clearScopedSession();
+    }
+  }
+
   /**
    *
    * This performs an operation on the session object, limited to a single user entry.  The state of that