public Builder identitySource(String identitySource) {
            this.identitySource = identitySource;
            return this;
        }
Sets the comma-separated list of mapping expressions of the request
parameters as the identity source.

<p>This property is only applicable for the authorizer of the
"request" type only.

@param identitySource Identity source CSV to set.
@return Returns the builder.
smithy-aws-apigateway-traits/src/main/java/software/amazon/smithy/aws/apigateway/traits/AuthorizerDefinition.java