⚡ Extend googleApi credentials to support user impersonification (#1304)

* ⚡ Extend googleApi credentials to support user impersonification

* ⚡ Add service account authentication to Gmail

* ⚡ Minor improvements

Co-authored-by: Jan Oberhauser <jan.oberhauser@gmail.com>

packages/nodes-base/credentials/GoogleApi.credentials.ts

@@ -10,7 +10,7 @@ export class GoogleApi implements ICredentialType {
 	documentationUrl = 'google';
 	properties = [
 		{
-			displayName: 'Email',
+			displayName: 'Service Account Email',
 			name: 'email',
 			type: 'string' as NodePropertyTypes,
 			default: '',
@@ -25,5 +25,25 @@ export class GoogleApi implements ICredentialType {
 			default: '',
 			description: 'Use the multiline editor. Make sure there are exactly 3 lines.<br />-----BEGIN PRIVATE KEY-----<br />KEY IN A SINGLE LINE<br />-----END PRIVATE KEY-----',
 		},
+		{
+			displayName: ' Impersonate a User',
+			name: 'inpersonate',
+			type: 'boolean' as NodePropertyTypes,
+			default: false,
+		},
+		{
+			displayName: 'Email',
+			name: 'delegatedEmail',
+			type: 'string' as NodePropertyTypes,
+			default: '',
+			displayOptions: {
+				show: {
+					inpersonate: [
+						true,
+					],
+				},
+			},
+			description: 'The email address of the user for which the application is requesting delegated access.',
+		},
 	];
 }