Till now, the REST API application we've been developing has used a simple api key passed in as a URL parameter, but we've just switched to using the OAuth2 Client Credentials Flow.
This is the simple workflow in which a client POSTs a key and secret via basic authentication and receives an expiring access token. Unfortunately, simple as it is, it's made it considerably more difficult to do quick tests of the API in a browser, either during development or for our support team to do installation sanity checks.
I've tried OAuth 2.0 Playground and REST Console for Chrome, but both of these only seem to support the more complex Authorization Code Grant workflow. Is there a browser-based tool that supports the Client Credentials flow?