Bugfix/eodhp 549 fastapi ensure next link only included when subsequent results exist

[tjellicoe-tpzuk]

Update STAC-FastApi to Only Return Tokens for Pagination when Subsequent Results are Available

• Update token logic to only return token when mroe results are available in elasticsearch
  • Logic borrows from a later commit to the STAC-FastApi repository
• Updated token handling for access-control to return the token for the last result returned to allow pagination to continue based on last accessible result, rather than last ES response
  • The tokens for each ES result are returned from certain functions to allow STAC-FastApi to return the token for the last result returned after the access-control layer has filtered the responses
  • This allows pagination to continue from the latest access-controlled entry, rather than from the latest ES token

This PR is to be merged into the EODHP-481 branch as this also includes updates to pagination logic and this helps to consolidate code changes together.

[ahaywardtvuk]

I don't know the code well enough to review in detail this sprint, so my only comment is on the left-over debugging 'print's.

[ahaywardtvuk]

These print statements seem to be left over from debugging and can be removed now.

[tjellicoe-tpzuk]

Good spot, removed unnecessary print statements