Update System Status page to include Postgres

[christhepianist]

Descriptive summary

Hyku version 6.0 + commits through cf5a4fc

Rationale

Currently, the options for System Status include Fedora, Solr, Redis and Database. With Valkyrie, Fedora is irrelevant, but adding Postgres would be a good replacement.

Expected behavior

Postgres status would be added to the list. Fedora could either be removed for those with Valkyrie, or there could be a note stating that it is not used in this environment. For Fedora users, Postgres would either be removed or could have the same note.

Actual behavior

In our Valkyrie implementation, we can see system statuses for Fedora, Solr, Redis and Database. Fedora says it is "OK," but since we don't use Fedora, this status is incorrect.

Steps to reproduce the behavior

1. Open Hyku 6.x under Valkyrie
2. Open System Status

Related work

Link to related tickets or prior related work here.