Add UI logic to support OAuth authentication flow

Add support in credentialsList to kickoff an OAuth2 authorization
flow. This enables users to authenticate and allow n8n to store
the resulting keys in the backend.

packages/editor-ui/src/components/mixins/restApi.ts

@@ -252,6 +252,21 @@ export const restApi = Vue.extend({
 					return self.restApi().makeRestApiRequest('GET', `/credential-types`);
 				},
 
+				// Get OAuth2 Authorization URL using the stored credentials
+				OAuth2CredentialAuthorize: (sendData: ICredentialsResponse): Promise<string> => {
+					return self.restApi().makeRestApiRequest('GET', `/oauth2-credential/auth`, sendData);
+				},
+
+				// Verify OAuth2 provider callback and kick off token generation
+				OAuth2Callback: (code: string, state: string): Promise<string> => {
+					const sendData = {
+						'code': code,
+						'state': state
+					};
+
+					return self.restApi().makeRestApiRequest('POST', `/oauth2-credential/callback`, sendData);
+				},
+
 				// Returns the execution with the given name
 				getExecution: async (id: string): Promise<IExecutionResponse> => {
 					const response = await self.restApi().makeRestApiRequest('GET', `/executions/${id}`);