Cannot use unix socket URI without authority for redis cache

[RuairidhWilliamson]

The documentation https://github.com/mozilla/sccache/blob/main/docs/Redis.md states you can use a unix socket endpoint of unix:///tmp/redis.sock. However this gives the error endpoint is invalid, source: invalid format.

This is because the URI is parsed by http::Uri which has a known limitation that it does not parse URIs without authorities. hyperium/http#323

As a work around you can put any authority e.g. unix://banana/tmp/redis.sock. This will parse correctly and the authority is ignored by sccache anyway.