feat: custom branding (#112)

* add first concept

* remove setup status

* split config page in multiple components

* add custom branding docs

* add test email button

* fix invalid email from header

* add migration

* mount images to host

* update docs

* remove unused endpoint

* run formatter

backend/src/auth/auth.controller.ts

@@ -42,7 +42,7 @@ export class AuthController {
     @Body() dto: AuthRegisterDTO,
     @Res({ passthrough: true }) response: Response
   ) {
-    if (!this.config.get("ALLOW_REGISTRATION"))
+    if (!this.config.get("share.allowRegistration"))
       throw new ForbiddenException("Registration is not allowed");
 
     const result = await this.authService.signUp(dto);