helm: add collabora.config and configFromSecrets values

[Rash419]

A single unstructured extra_params string of --o: flags does not scale and cannot carry secrets. collabora.config is a flat map of coolwsd setting paths rendered into the ConfigMap and mounted at /etc/coolwsd/overrides.d, where coolwsd of version 26.04 or later picks it up. The map is flat because index and attribute syntax like monitors.monitor[0][@retryInterval] has no natural nested YAML form, and flat keys can be copied straight from an existing extra_params.

collabora.configFromSecrets binds setting paths to Kubernetes Secrets. It is a map keyed by the setting path, because helm merges maps per key across values files while lists are replaced wholesale. With create true the chart creates the Secret from the given value, and rotation rolls the pods through the confighash annotation. With create false an existing Secret is referenced. Either way coolwsd reads the value from the mounted file, so it never appears in the ConfigMap, the pod spec or the logs.

Entries are validated at template time: setting paths that would break the key=value file format, values with newlines, invalid Secret names and keys, and the admin_console credentials, which the chart always injects as environment variables that would override the new layer anyway.

extra_params keeps working and stays the default for ssl.enable=false because the current appVersion image does not read overrides.d yet. Flip the default to config once appVersion is on 26.04.

Change-Id: I2b1f12ec829519d1aa4f142e1e4ad14d4a702ff6

Depends on gerrit change: https://gerrit.collaboraoffice.com/c/online/+/4270/2

[timar]

I'm sorry @Rash419 I did not notice this PR, and it cannot be rebased to main without conflicts. Please rebase it, and ping me again.