Feature s3 write csv

[zorge69]

Description

Added write_csv to save a Pandas df to s3 bucket using boto3 client.

Added a function write_csv to rdsa_utils\cdp\helpers\s3_utils.py. This function utilises Pandas to_csv method and can potentially take any keyword arguments of it. The content of the dataframe is initially serialised into a StringIO buffer. Then, we use the boto3 client's method put_object. Unit-testing is done using the mocking, via moto library. Three unit tests are added: that True is returned if successful, that the written CSV can be read back and gives the same dataframe, and a negative test, such as if it fails, False is returned. The failure is realised by trying to apply to_csv to a dictionary, which does not have this method.

This pr introduces....

Type of change

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• New feature - non-breaking change

Checklist:

• I have performed a self-review of my own code.
• I have commented my code appropriately, focusing on explaining my design decisions (explain why, not how).
• I have made corresponding changes to the documentation (comments, docstring, etc.. )
• I have added tests that prove my fix is effective or that my feature works.
• New and existing unit tests pass locally with my changes.
• I have updated the change log.

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• Documentation: docstrings, comments have been added/ updated.
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• Complexity: The code is not overly complex, logic has been split into appropriately sized functions, etc..
• Test coverage: Unit tests cover essential functions for a reasonable range of inputs and conditions. Added and existing tests pass on my machine.

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