Make bearer prefix on auth header case insensitive

From a support ticket:

> the "Bearer" prefix on the auth header is case sensitive. Can this be
> made case-insensitive?

Sure can 🙃

app/authentication/auth.py

@@ -27,7 +27,7 @@ def get_auth_token(req):
     if not auth_header:
         raise AuthError('Unauthorized, authentication token must be provided', 401)
 
-    auth_scheme = auth_header[:7]
+    auth_scheme = auth_header[:7].title()
 
     if auth_scheme != 'Bearer ':
         raise AuthError('Unauthorized, authentication bearer scheme must be used', 401)