This updates access check requests to ensure the requested action exists
in the policy for the provided resource beforce executing the request to
spicedb and failing for this error.

Knowing this we can return a relevant error (ErrInvalidAction) which we
can now handle and return a 400 Bad Request status code instead of the
previous 500 Internal Server Error status code we were returning due to
the spicedb error we were receiving before.

Signed-off-by: Mike Mason <[email protected]>

Context Canceled errors from http requests should not produce 500 errors
as those are client requests.
This change adds an error middleware which can capture the canceled
context error and return a 422 status instead.

Signed-off-by: Mike Mason <[email protected]>

This validates create/update role action requests before submitting the
request to spicedb and handles the errors gracefully by returning 400
errors instead of generic 500 errors to the client.

Signed-off-by: Mike Mason <[email protected]>

This handles role http endpoint errors better by better handling the
errors returned and setting the response status codes.

Additionally this adds testing to the http api so we may test these http
status codes to ensure they are working as we expect.

Signed-off-by: Mike Mason <[email protected]>

This adds http tests and fixes the http status codes for the role
assignment and unassignment endpoints to resolve 500 errors occurring
when provided role ids were didn't exist.

Signed-off-by: Mike Mason <[email protected]>