(core) Admin Panel and InstallAdmin class to identify installation admins.

Summary:
- Add InstallAdmin class to identify users who can manage Grist installation.

  This is overridable by different Grist flavors (e.g. different in SaaS).
  It generalizes previous logic used to decide who can control Activation
  settings (e.g. enable telemetry).

- Implement a basic Admin Panel at /admin, and move items previously in the
  "Support Grist" page into the "Support Grist" section of the Admin Panel.

- Replace "Support Grist" menu items with "Admin Panel" and show only to admins.

- Add "Support Grist" links to Github sponsorship to user-account menu.

- Add "Support Grist" button to top-bar, which
  - for admins, replaces the previous "Contribute" button and reopens the "Support Grist / opt-in to telemetry" nudge (unchanged)
  - for everyone else, links to Github sponsorship
  - in either case, user can dismiss it.

Test Plan: Shuffled some test cases between Support Grist and the new Admin Panel, and added some new cases.

Reviewers: jarek, paulfitz

Reviewed By: jarek, paulfitz

Differential Revision: https://phab.getgrist.com/D4194

app/common/UserAPI.ts

@@ -243,8 +243,13 @@ export function getUserRoleText(user: UserAccessData) {
   return roleNames[user.access!] || user.access || 'no access';
 }
 
+export interface ExtendedUser extends FullUser {
+  helpScoutSignature?: string;
+  isInstallAdmin?: boolean;     // Set if user is allowed to manage this installation.
+}
+
 export interface ActiveSessionInfo {
-  user: FullUser & {helpScoutSignature?: string};
+  user: ExtendedUser;
   org: Organization|null;
   orgError?: OrgError;
 }

app/common/gristUrls.ts

@@ -44,8 +44,8 @@ export type ActivationPage = typeof ActivationPage.type;
 export const LoginPage = StringUnion('signup', 'login', 'verified', 'forgot-password');
 export type LoginPage = typeof LoginPage.type;
 
-export const SupportGristPage = StringUnion('support');
-export type SupportGristPage = typeof SupportGristPage.type;
+export const AdminPanelPage = StringUnion('admin');
+export type AdminPanelPage = typeof AdminPanelPage.type;
 
 // Overall UI style.  "full" is normal, "singlePage" is a single page focused, panels hidden experience.
 export const InterfaceStyle = StringUnion('singlePage', 'full');
@@ -124,7 +124,7 @@ export interface IGristUrlState {
   activation?: ActivationPage;
   login?: LoginPage;
   welcome?: WelcomePage;
-  supportGrist?: SupportGristPage;
+  adminPanel?: AdminPanelPage;
   welcomeTour?: boolean;
   docTour?: boolean;
   manageUsers?: boolean;
@@ -309,7 +309,7 @@ export function encodeUrl(gristConfig: Partial<GristLoadConfig>,
     parts.push(`welcome/${state.welcome}`);
   }
 
-  if (state.supportGrist) { parts.push(state.supportGrist); }
+  if (state.adminPanel) { parts.push(state.adminPanel); }
 
   const queryParams = pickBy(state.params, (v, k) => k !== 'linkParameters') as {[key: string]: string};
   for (const [k, v] of Object.entries(state.params?.linkParameters || {})) {
@@ -415,7 +415,7 @@ export function decodeUrl(gristConfig: Partial<GristLoadConfig>, location: Locat
   // the minimum length of a urlId prefix is longer than the maximum length
   // of any of the valid keys in the url.
   for (const key of map.keys()) {
-    if (key.length >= MIN_URLID_PREFIX_LENGTH && !LoginPage.guard(key) && !SupportGristPage.guard(key)) {
+    if (key.length >= MIN_URLID_PREFIX_LENGTH && !LoginPage.guard(key)) {
       map.set('doc', key);
       map.set('slug', map.get(key)!);
       map.delete(key);
@@ -453,9 +453,7 @@ export function decodeUrl(gristConfig: Partial<GristLoadConfig>, location: Locat
     state.activation = ActivationPage.parse(map.get('activation')) || 'activation';
   }
   if (map.has('welcome')) { state.welcome = WelcomePage.parse(map.get('welcome')); }
-  if (map.has('support')) {
-    state.supportGrist = SupportGristPage.parse(map.get('support')) || 'support';
-  }
+  if (map.has('admin')) { state.adminPanel = AdminPanelPage.parse(map.get('admin')) || 'admin'; }
   if (sp.has('planType')) { state.params!.planType = sp.get('planType')!; }
   if (sp.has('billingPlan')) { state.params!.billingPlan = sp.get('billingPlan')!; }
   if (sp.has('billingTask')) {
@@ -740,7 +738,7 @@ export interface GristLoadConfig {
   // Google Tag Manager id. Currently only used to load tag manager for reporting new sign-ups.
   tagManagerId?: string;
 
-  activation?: Activation;
+  activation?: ActivationState;
 
   // List of enabled features.
   features?: IFeature[];
@@ -799,6 +797,7 @@ export const Features = StringUnion(
   "multiAccounts",
   "sendToDrive",
   "tutorials",
+  "supportGrist",
 );
 export type IFeature = typeof Features.type;
 
@@ -834,10 +833,6 @@ export interface ActivationState {
   }
 }
 
-export interface Activation extends ActivationState {
-  isManager: boolean;
-}
-
 // Acceptable org subdomains are alphanumeric (hyphen also allowed) and of
 // non-zero length.
 const subdomainRegex = /^[-a-z0-9]+$/i;