[management,proxy,client] Add L4 capabilities (TLS/TCP/UDP) (#5530)

management/internals/modules/reverseproxy/domain/domain.go

@@ -14,6 +14,9 @@ type Domain struct {
 	TargetCluster string // The proxy cluster this domain should be validated against
 	Type          Type   `gorm:"-"`
 	Validated     bool
+	// SupportsCustomPorts is populated at query time for free domains from the
+	// proxy cluster capabilities. Not persisted.
+	SupportsCustomPorts *bool `gorm:"-"`
 }
 
 // EventMeta returns activity event metadata for a domain