feat(core): Add Support for Additional Body Properties in OAuth2 API Client Credentials Flow (#16573)

Co-authored-by: Elias Meire <elias@meire.dev>

packages/core/src/execution-engine/node-execution-context/utils/request-helper-functions.ts

@@ -929,6 +929,22 @@ export function applyPaginationRequestData(
 	return merge({}, requestData, preparedPaginationData);
 }
 
+function createOAuth2Client(credentials: OAuth2CredentialData): ClientOAuth2 {
+	return new ClientOAuth2({
+		clientId: credentials.clientId,
+		clientSecret: credentials.clientSecret,
+		accessTokenUri: credentials.accessTokenUrl,
+		scopes: (credentials.scope as string).split(' '),
+		ignoreSSLIssues: credentials.ignoreSSLIssues,
+		authentication: credentials.authentication ?? 'header',
+		...(credentials.additionalBodyProperties && {
+			additionalBodyProperties: jsonParse(credentials.additionalBodyProperties, {
+				fallbackValue: {},
+			}),
+		}),
+	});
+}
+
 /** @deprecated make these requests using httpRequestWithAuthentication */
 export async function requestOAuth2(
 	this: IAllExecuteFunctions,
@@ -950,14 +966,7 @@ export async function requestOAuth2(
 		throw new ApplicationError('OAuth credentials not connected');
 	}
 
-	const oAuthClient = new ClientOAuth2({
-		clientId: credentials.clientId,
-		clientSecret: credentials.clientSecret,
-		accessTokenUri: credentials.accessTokenUrl,
-		scopes: (credentials.scope as string).split(' '),
-		ignoreSSLIssues: credentials.ignoreSSLIssues,
-		authentication: credentials.authentication ?? 'header',
-	});
+	const oAuthClient = createOAuth2Client(credentials);
 
 	let oauthTokenData = credentials.oauthTokenData as ClientOAuth2TokenData;
 	// if it's the first time using the credentials, get the access token and save it into the DB.

packages/nodes-base/credentials/OAuth2Api.credentials.ts

@@ -107,6 +107,34 @@ export class OAuth2Api implements ICredentialType {
 			],
 			default: 'header',
 		},
+		{
+			displayName: 'Send Additional Body Properties',
+			name: 'sendAdditionalBodyProperties',
+			type: 'boolean',
+			default: false,
+			displayOptions: {
+				show: {
+					grantType: ['clientCredentials'],
+					authentication: ['body'],
+				},
+			},
+		},
+		{
+			displayName: 'Additional Body Properties',
+			name: 'additionalBodyProperties',
+			type: 'json',
+			typeOptions: {
+				rows: 5,
+			},
+			displayOptions: {
+				show: {
+					grantType: ['clientCredentials'],
+					authentication: ['body'],
+					sendAdditionalBodyProperties: [true],
+				},
+			},
+			default: '',
+		},
 		{
 			displayName: 'Ignore SSL Issues (Insecure)',
 			name: 'ignoreSSLIssues',