Encrypt Query Params in Page Links

[alexanderkiel]

Currently, the page links contain the database point in time t of the database state on which the FHIR search query was executed, the query params of the FHIR search and the id of the resource on top of the page. All this information can be manipulated by the client.

Especially, by changing the t the client can access past database states that still contain possibly deleted resources. After we implement #1382, the deleted historic versions of a resource will be no longer accessible in the database state after the delete, but will be still accessible in former database states. That's why it's important that a client can't simply edit the t in page links.

See also: Paging Documentation