Refactor update creation api

This merge request does the following:

• Raise DRF errors rather than returning response to take advantage of the DRF exception handling mechanism
• Create serialisers for PUT request to simplify the code
• Improve validation checks in several places
• Fixes several issues in DRF infrastructure uses
• Fixes JSON fields handling
• Remove routes that do no fully qualify objects
• Implement a custom DRF exception handler that will allow to log errors
• Improve testing
• Improve permission management

beat/web/common/utils.py

@@ -135,3 +135,13 @@ def ensure_string(data):
             return data.decode("utf-8")
         return data
     return ""
+
+
+def py3_cmp(a, b):
+    """
+    cmp is not available anymore in Python 3. This method is implemetend
+    as recommended in the documentation for this kind of use case.
+    Based on:
+      https://docs.python.org/3.0/whatsnew/3.0.html#ordering-comparisons
+    """
+    return (a > b) - (a < b)