Drf-json-api-atomic-operations

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Added
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* bulk operating for `add` and `delete` operations

Fixed
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* adds `check_resource_identifier_object` check on parser to check update operation correctly

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Added
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* to-one relationship update
* to-many relationship update

Fixed
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* fixes some json pointers for some parse errors


Changed
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* implemented custom exception classes to simplify code
* uses constant string values to reduce code duplications

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Added
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* sequential handling for add, update and remove operation code
* detailed error responses with indexed source pointing