Update parsing logic to account for recent changes to input JSON file format.

[JCantu248]

🗣 Description

The RPT has updated the format of their JSON data that provides input to TPT-Reports. The source for TPT-Reports has been updated to reflect these changes. The payloads list has been nested under the phishing_assessment property. In addition, the assessment ID number is provided in the new format, so it is no longer necessary as a command line argument and has been removed.

All test cases have been updated to reflect these new changes. Resolves issue #66

💭 Motivation and context

This change is required so the PCA team can use TPT-Reports with the latest RPT JSON format.

🧪 Testing

Test cases have been updated and verified with PyTest.

✅ Pre-approval checklist

• [x] This PR has an informative and human-readable title.
• [x] Changes are limited to a single goal - eschew scope creep!
• [x] All future TODOs are captured in issues, which are referenced in code comments.
• [x] All relevant type-of-change labels have been added.
• [x] I have read the CONTRIBUTING document.
• [x] These code changes follow cisagov code standards.
• [x] All relevant repo and/or project documentation has been updated to reflect the changes in this PR.
• [x] Tests have been added and/or modified to cover the changes in this PR.
• [x] All new and existing tests pass.

✅ Pre-merge checklist

• [x] Revert dependencies to default branches.
• [x] Finalize version.

✅ Post-merge checklist

• [x] Create a release.

[coveralls]

Pull Request Test Coverage Report for Build 6775873184

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 0.0%

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Totals
Change from base Build 6737391088:	0.0%
Covered Lines:	0
Relevant Lines:	0

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💛 - Coveralls