Feature-87: `delete_object` Refactor & Enhancements

[doulikecookiedough]

Summary of Changes:

• Updated object_metadata class with new attribute pid to help client streamline the process of passing a pid value.
• Metadata Public API Method Updates:
  • Refactored store_metadata to follow new metadata storage design, where all metadata documents for a given pid live in a directory formed by calculating the hash of the pid, with the document name being the hash of the pid + format_id
  • Updated retrieve_metadata and delete_metadata to account for above changes.
  • delete_metadata will remove all metadata documents for a given pid if no format_id is provided
• Public API Method delete_object Updates:
  • Deleting an object will also remove all metadata associated with a given pid
  • Addressed situations involving orphaned pid references files by handling exceptions where relevant
  • Improved atomicity of deletion by renaming all files (appending _delete to the file name), adding them to a list, and then iterating over that list to delete files.
• Refactored methods related to creating reference files to improve clarity
• Updated documentation

[doulikecookiedough]

Greetings @artntek, when you have a moment - can you please help me review this branch?

[doulikecookiedough]

I am merging this PR into develop as I have addressed @artntek's review comments. @jeanetteclark who will be testing HashStore in the coming weeks will provide further feedback.