### Description of the change
Based on the discussion under https://gitea.com/gitea/helm-gitea/issues/60, it is possible to use `gitea.additionalConfigFromEnvs` to provide variables in order to override configurations from `app.ini`.
Especially when using gitea as a dependency of an umbrella, some values may need to be repeated in multiple places (such has database configuration). Hence, introducing the `tpl` function on `gitea.additionalConfigFromEnvs` will simplify such repetition by having the value only set in one place...
### Benefits
With the same intentions as https://gitea.com/gitea/helm-gitea/pulls/759, https://gitea.com/gitea/helm-gitea/pulls/664, https://gitea.com/gitea/helm-gitea/pulls/529 or https://gitea.com/gitea/helm-gitea/pulls/498, this change will allow reusing the value from other value parameters to avoid duplicating the same value in multiple places.
### Possible drawbacks
N/A
### Applicable issues
N/A
### Additional information
N/A
### Checklist
- [X] Helm templating unittests are added (required when changing anything in `templates` folder)
Co-authored-by: 212597596 <cedric.henry@ge.com>
Co-authored-by: pat-s <pat-s@noreply.gitea.com>
Reviewed-on: https://gitea.com/gitea/helm-gitea/pulls/840
Reviewed-by: pat-s <pat-s@noreply.gitea.com>
Reviewed-by: justusbunsi <justusbunsi@noreply.gitea.com>
Co-authored-by: Ceddaerrix <ceddaerrix@noreply.gitea.com>
Co-committed-by: Ceddaerrix <ceddaerrix@noreply.gitea.com>
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