started with Multi-Tenant OpenID.

TODO:
working code but needs some refactoring and cleaning up.

api/server/utils/openidHelper.js

@@ -0,0 +1,52 @@
+const { logger } = require('~/config');
+const { getCustomConfig } = require('~/server/services/Config');
+
+/**
+ * Loads the tenant configurations from the custom configuration.
+ * @returns {Promise<Array>} Array of tenant configurations.
+ */
+async function getOpenIdTenants() {
+  try {
+    const customConfig = await getCustomConfig();
+    if (customConfig?.openid?.tenants) {
+      return customConfig.openid.tenants;
+    }
+  } catch (err) {
+    logger.error('Failed to load custom configuration for OpenID tenants:', err);
+  }
+  return [];
+}
+
+/**
+ * Chooses the OpenID strategy name based on the email domain.
+ * It consults the global tenant mapping (built in setupOpenId).
+ * @param {import('express').Request} req - The Express request object.
+ * @returns {Promise<string>} - The chosen strategy name.
+ */
+async function chooseOpenIdStrategy(req) {
+  if (req.query.email) {
+    const email = req.query.email;
+    const domain = email.split('@')[1].toLowerCase();
+    const tenants = await getOpenIdTenants();
+
+    // Iterate over the tenants and return the strategy name of the first matching tenant
+    for (const tenant of tenants) {
+      if (tenant.domains) {
+        const tenantDomains = tenant.domains.split(',').map(s => s.trim().toLowerCase());
+        if (tenantDomains.includes(domain)) {
+          // Look up the registered strategy via the global mapping.
+          if (tenant.name && tenant.name.trim() && global.__openidTenantMapping) {
+            const mapped = global.__openidTenantMapping.get(tenant.name.trim().toLowerCase());
+            if (mapped) {
+              return mapped;
+            }
+          }
+          return 'openid'; // Fallback if no mapping exists.
+        }
+      }
+    }
+  }
+  return 'openid';
+}
+
+module.exports = { getOpenIdTenants, chooseOpenIdStrategy };