[management, proxy] Add require_subdomain capability for proxy clusters (#5628)

shared/management/http/api/openapi.yml

@@ -3336,6 +3336,10 @@ components:
           type: boolean
           description: Whether the cluster supports binding arbitrary TCP/UDP ports
           example: true
+        require_subdomain:
+          type: boolean
+          description: Whether a subdomain label is required in front of this domain. When true, the domain cannot be used bare.
+          example: false
       required:
         - id
         - domain

shared/management/http/api/types.gen.go

@@ -3406,6 +3406,9 @@ type ReverseProxyDomain struct {
 	// Id Domain ID
 	Id string `json:"id"`
 
+	// RequireSubdomain Whether a subdomain label is required in front of this domain. When true, the domain cannot be used bare.
+	RequireSubdomain *bool `json:"require_subdomain,omitempty"`
+
 	// SupportsCustomPorts Whether the cluster supports binding arbitrary TCP/UDP ports
 	SupportsCustomPorts *bool `json:"supports_custom_ports,omitempty"`