Changes Made

• Move cursor computing logic to functions on a new file under the utils folder.
• Add the includeCursor opt-in param.
• Compute cursor for each result (resolves [Feature Proposal] Compute cursor for each document #156) based on the includeCursor param.

Potential Risks

Not fully understanding all the uses of the paginatedField, I just isolated and exctracted the cursor creation logic from existing code I found on this library. If something I didn't predict is passed in the paginatedField value, the cursor validity would be compromised. The good thing is that the new centralized approach handles the cursor logic isolatedly so this event would be easier to spot and fix.

Test Plan

• Existing code using this library shouldn't see any changes.
• By passing the new includeCursor parameter, the response should include a _cursor property for each document, containing the document cursor.
• The first document cursor should be equal to the previous result property.
• The last document cursor should be equal to the next result property.
• Being the result empty, the previous and next results should be null.

Checklist

• I've increased test coverage
• Since this is a public repository, I've checked I'm not publishing private data in the code, commit comments, or this PR.