feat(facebook): add support for business login using config ids (#1990)

docs/content/docs/authentication/facebook.mdx

@@ -34,6 +34,11 @@ description: Facebook provider setup and usage.
             },
         })
         ```
+
+        <Callout>
+        BetterAuth also supports Facebook Login for Business, all you need
+        to do is provide the `configId` as listed in **Facebook Login For Business > Configurations** alongside your `clientId` and `clientSecret`. Note that the app must be a Business app and, since BetterAuth expects to have an email address and account id, the configuration must be of the "User access token" type. "System-user access token" is not supported.
+        </Callout>
     </Step>
        <Step>
         ### Sign In with Facebook

packages/better-auth/src/social-providers/facebook.ts

@@ -25,6 +25,11 @@ export interface FacebookOptions extends ProviderOptions<FacebookProfile> {
 	 * @default ["id", "name", "email", "picture"]
 	 */
 	fields?: string[];
+
+	/**
+	 * The config id to use when undergoing oauth
+	 */
+	configId?: string;
 }
 
 export const facebook = (options: FacebookOptions) => {
@@ -45,6 +50,11 @@ export const facebook = (options: FacebookOptions) => {
 				state,
 				redirectURI,
 				loginHint,
+				additionalParams: options.configId
+					? {
+							config_id: options.configId,
+						}
+					: {},
 			});
 		},
 		validateAuthorizationCode: async ({ code, redirectURI }) => {