Constellation, Spacedust, Slingshot, UFOs: atproto crates and services for microcosm

Convert existing REST /links/distinct-dids endpoint to XRPC equivalent #8 #48

Merged microcosm.blue
targeting main from deleted fork:xrpc_get_distinct
Merged opened by and assigned to microcosm.blue
targeting main from deleted fork:xrpc_get_distinct

Simple conversion of the existing endpoint from REST to XRPC. Consecutively marked the pre-existing REST endpoint as deprecated.

Commits 0