Enable admin port

[stranljip]

I was trying to make a release and discovered that the readiness probe failed because it returned HTTP 401. In order to address this I have enabled the admin port (see https://postgrest.org/en/stable/references/admin.html#health-check) and set the readiness probe to use that port (/live). I have disabled the possibility to set a custom readinessprobe - not sure if this should stay like this or if it should be optional

[colearendt]

I think this is a great idea! Unfortunately there are a few things about the implementation that are preferable on a public chart:

• values should be defined in values.yaml
• it is totally reasonable to change the defaults, but you should still leave the defaults in values.yaml so that users can modify if needed
• per docs here, I think /ready is more consistent with a readinessProbe. However, you can change to /live in your deployment if you want using the values

I took the liberty of fixing this in #59 😄 Thanks!