#159222976 Add id nonce to ensure new entry Id uniqueness

[olusoladavid]

What does this PR do?

Fixes bug that results from deleting an entry and adding a new entry in the previous build. Adding a new entry after a deletion results in entries with the same ids. This bug has been corrected with the use of an id nonce for generating ids for new entries.

Description of Task to be completed

• Add idNonce variable that always increments for every new entry added
• Increment idNonce when user adds a new entry
• Assign id to new entry based on the id of idNonce's count property.
• Integrate idNonce in tests

How should this be manually tested?

API endpoint has been deployed to: https://my-diary-api.herokuapp.com/api/v1

Using Postman:

1. Send a GET request to /entries to retrieve a list of all available entries
2. Send a DELETE request to /entries/:id for one of the available entries
3. Send a POST request to /entries with body
   { "timestamp": 153462783, "title": "title", "content": "content", "isFavorite": true }
4. Repeat step 1 and review the results.

What are the relevant pivotal tracker stories?

#159222976

[coveralls]

Pull Request Test Coverage Report for Build 34

• 3 of 3 (100.0%) changed or added relevant lines in 2 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 100.0%

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Totals
Change from base Build 32:	0.0%
Covered Lines:	51
Relevant Lines:	51

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💛 - Coveralls