fix: Do not show actively disabled auth providers in self-hosted install (#4794)

* fix: Do not show actively disabled auth providers in self-hosted installation

* self review

* Refactor for easier mocking

server/models/helpers/AuthenticationHelper.ts

@@ -0,0 +1,42 @@
+import { find } from "lodash";
+import env from "@server/env";
+import Team from "@server/models/Team";
+import providerConfigs from "../../routes/auth/providers";
+
+export default class AuthenticationHelper {
+  /**
+   * Returns the enabled authentication provider configurations for a team,
+   * if given otherwise all enabled providers are returned.
+   *
+   * @param team The team to get enabled providers for
+   * @returns A list of authentication providers
+   */
+  static providersForTeam(team?: Team) {
+    const isCloudHosted = env.isCloudHosted();
+
+    return providerConfigs
+      .sort((config) => (config.id === "email" ? 1 : -1))
+      .filter((config) => {
+        // guest sign-in is an exception as it does not have an authentication
+        // provider using passport, instead it exists as a boolean option on the team
+        if (config.id === "email") {
+          return team?.emailSigninEnabled;
+        }
+        if (!team) {
+          return true;
+        }
+
+        const authProvider = find(team.authenticationProviders, {
+          name: config.id,
+        });
+
+        // If cloud hosted then the auth provider must be enabled for the team,
+        // If self-hosted then it must not be actively disabled, otherwise all
+        // providers are considered.
+        return (
+          (!isCloudHosted && authProvider?.enabled !== false) ||
+          (isCloudHosted && authProvider?.enabled)
+        );
+      });
+  }
+}