### Description of the change
Adding support for DRY principle (via use of the TPL function) to the PVC storage class and the ingress class
### Benefits
It allows to reference a variable into another one to avoid duplicating them (or using YAML anchors).
It is useful and valuable when including Gitea into an umbrella chart with multiple components and to have a single variable while the components variable only refer to that single one.
Example 1
```
global:
persistence:
storageClass: "storage-class"
persistence:
storageClass: "{{ .Values.global.persistence.storageClass }}"
```
This results in having `spec.storageClassName` equal to `storage-class` in the PVC object
Example 2
```
global:
ingress:
className: "ingress-class"
ingress:
className: "{{ .Values.global.ingress.className}}"
```
This results in having `spec.ingressClassName` equal to `ingress-class` in the Ingress object
### Possible drawbacks
N/A
### Checklist
- [X] Templating unittests are added
Co-authored-by: 212597596 <cedric.henry@ge.com>
Co-authored-by: pat-s <pat-s@noreply.gitea.com>
Co-authored-by: justusbunsi <justusbunsi@noreply.gitea.com>
Reviewed-on: https://gitea.com/gitea/helm-chart/pulls/664
Reviewed-by: pat-s <pat-s@noreply.gitea.com>
Co-authored-by: Ceddaerrix <ceddaerrix@noreply.gitea.com>
Co-committed-by: Ceddaerrix <ceddaerrix@noreply.gitea.com>
