Break up Credential type into two interfaces

Author: mbg

src/start-proxy/types.ts

@@ -1,8 +1,11 @@
-export type Credential = {
-  type: string;
-  host?: string;
-  url?: string;
+export interface Credential extends Registry {
   username?: string;
   password?: string;
   token?: string;
-};
+}
+
+export interface Registry {
+  type: string;
+  host?: string;
+  url?: string;
+}