Improve registration page and add a rules option

Signed-off-by: Thomas Citharel <tcit@tcit.fr>

js/src/types/admin.model.ts

@@ -20,5 +20,6 @@ export interface IAdminSettings {
   instanceTerms: string;
   instanceTermsType: InstanceTermsType;
   instanceTermsUrl: string | null;
+  instanceRules: string;
   registrationsOpen: boolean;
 }

js/src/types/config.model.ts

@@ -59,6 +59,7 @@ export interface IConfig {
     type: InstanceTermsType;
     url: string;
   };
+  rules: string;
   resourceProviders: IProvider[];
   timezones: string[];
   features: {