feat: add external property to coder_app (#5425)

* Add schema

* feat: add `external` property to `coder_app`

This allows exposing applications that open an external URL.

codersdk/workspaceapps.go

@@ -23,6 +23,12 @@ const (
 
 type WorkspaceApp struct {
 	ID uuid.UUID `json:"id"`
+	// URL is the address being proxied to inside the workspace.
+	// If external is specified, this will be opened on the client.
+	URL string `json:"url"`
+	// External specifies whether the URL should be opened externally on
+	// the client or not.
+	External bool `json:"external"`
 	// Slug is a unique identifier within the agent.
 	Slug string `json:"slug"`
 	// DisplayName is a friendly name for the app.