Add the ability to load PG password from a secret

[xvilo]

I'm currently trying to set up a test instance of Uptrace with the helm chart. As I'm not statisfied with the supplied Postgres config, I'm configuring it to work with Zalando's Postgres Operator. Postgres Operator uses CRDs to define Postgres Clusters, Databases, Users, and access. In this case it will create a secret per user with the password. It would be very helpful if one is able to specifiy a secret for reference.

Kubectl example:

kubectl -n uptrace get secret
NAME                                                                     TYPE     DATA   AGE
postgres.uptrace-postgres-cluster.credentials.postgresql.acid.zalan.do   Opaque   2      4m47s
root.uptrace-postgres-cluster.credentials.postgresql.acid.zalan.do       Opaque   2      4m47s
standby.uptrace-postgres-cluster.credentials.postgresql.acid.zalan.do    Opaque   2      4m46s
uptrace.uptrace-postgres-cluster.credentials.postgresql.acid.zalan.do    Opaque   2      4m47s

Secret contents example:

apiVersion: v1
data:
  password: 64 bytes
  username: 7 bytes
kind: Secret
metadata:
  creationTimestamp: '2023-10-21T20:17:33Z'
  labels:
    application: spilo
    cluster-name: uptrace-postgres-cluster
    team: acid
[...]

Ideally, one wants to configure the secret name and the used key in the values. I created this issue for reference for now, might create a PR later 👍

[maxboone]

As an intermediate solution you could do something like:

env:
  - name: POSTGRES_USER
    valueFrom:
      secretKeyRef:
        name: uptrace.uptrace-postgres-cluster.credentials.postgresql.acid.zalan.do
        key: username
  - name: POSTGRES_PASS
    valueFrom:
      secretKeyRef:
        name: uptrace.uptrace-postgres-cluster.credentials.postgresql.acid.zalan.do
        key: password

config:
    pg:
      addr: postgresql:5432
      user: $POSTGRES_USER
      password: $POSTGRES_PASS
      database: uptrace

However, agreed that it would be better to allow more fine-grained helm templating of the configuration file and only use the config -> toYaml for stuff that needs to be hardcoded per se.

[vmihailenco]

Closing in favor of #29