Search - add relatedLink to Search Service results

[jonquandt]

Story

As a API user, I want to be able to see related documents for my search results so that I can grab related content easily.

example

For BILLS/BILLSTATUS/PLAW collection results

“relatedLink”:”https://api.govinfo.gov/related/BILLS-113hr1206enr"

For CFR/FR/CHRG

“relatedLink”:”https://api.govinfo.gov/related/CFR-2022-title47-vol3-sec61-46"

Acceptance Criteria

• search service responses would include a relatedLink key for all results that have defined relationships
• handle both related endpoints based on the packageId and granuleId, as appropriate for individual collections.