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/experiments/serializers.py

@@ -54,7 +54,7 @@ from .models import Experiment, Block
 class ExperimentCreationSerializer(serializers.ModelSerializer):
     declaration = beat_fields.JSONField()
     description = serializers.CharField(required=False, allow_blank=True)
-    fork_of = beat_fields.JSONField(required=False)
+    fork_of = serializers.CharField(required=False)
     toolchain = serializers.CharField()
 
     class Meta: