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/toolchains/serializers.py

@@ -42,7 +42,7 @@ import beat.core.toolchain
 class ToolchainCreationSerializer(ContributionCreationSerializer):
     class Meta(ContributionCreationSerializer.Meta):
         model = Toolchain
-        beat_core_class = beat.core.toolchain
+        beat_core_class = beat.core.toolchain.Toolchain
 
 
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