Links are overwritten when storing Item/Collection in database

[StijnCaerts]

Describe the bug
The links on Item and Collection objects are overwritten before persisting them in the database.

For Items, the links are overwritten in the ItemSerializer.stac_to_db() method:

stac-fastapi-elasticsearch-opensearch/stac_fastapi/core/stac_fastapi/core/serializers.py

Line 68 in 0c7cfcd

stac_data["links"] = item_links

For Collections, the links are overwritten in the TransactionsClient itself:

stac-fastapi-elasticsearch-opensearch/stac_fastapi/core/stac_fastapi/core/core.py

Line 737 in 0c7cfcd

collection["links"] = collection_links

To Reproduce
Steps to reproduce the behavior:

1. Create collection with links, eg. rel=license
2. Links are overwritten and the original links cannot be retrieved again when requesting the collection. They are also not persisted in the database.

Expected behavior

• Filter out INFERRED_LINK_RELS, store remaining links in the database
• Inferred links are added again when loading objects from database

[StijnCaerts]

Closed by #211