feat(chart): add dry support to "gitea.actions.local_root_url" function (#74)

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### Description of the change

Introducing use of the `tpl` function into _"gitea.actions.local_root_url"_ (in `_helpers.tpl`) so templating into the `giteaRootURL` parameter can be interpreted.
Hence, it will permit the use of values already set in other parameters.

### Benefits

To allow in an umbrella chart referencing to other values for setting the Gitea Root URL

### Possible drawbacks

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### Applicable issues

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- Fixes #

### Additional information

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### ⚠ BREAKING

 - N/A

### Checklist

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- [x] Helm templating unittests are added (required when changing anything in `templates` folder)

Co-authored-by: 212597596 <cedric.henry@gevernova.com>
Reviewed-on: https://gitea.com/gitea/helm-actions/pulls/74
Reviewed-by: DaanSelen <daanselen@noreply.gitea.com>
Co-authored-by: Ceddaerrix <ceddaerrix@noreply.gitea.com>
Co-committed-by: Ceddaerrix <ceddaerrix@noreply.gitea.com>

unittests/helm/statefulset.yaml

@@ -429,3 +429,35 @@ tests:
           content:
             mountPath: /mnt
             name: my-dind-volume
+  - it: should interpret Gitea Root URL templating
+    template: templates/statefulset.yaml
+    set:
+      global:
+        gitea:
+          service:
+            name: "my-gitea-svc-http"
+            port: 3210
+      enabled: true
+      giteaRootURL: "http://{{ .Values.global.gitea.service.name }}:{{ .Values.global.gitea.service.port }}"
+    asserts:
+      - hasDocuments:
+          count: 1
+      - containsDocument:
+          kind: StatefulSet
+          apiVersion: apps/v1
+          name: gitea-unittests-actions-act-runner
+      - equal:
+          path: spec.template.spec.containers[0].env[1].name
+          value: "GITEA_INSTANCE_URL"
+      - equal:
+          path: spec.template.spec.containers[0].env[1].value
+          value: "http://my-gitea-svc-http:3210"
+      - equal:
+          path: spec.template.spec.initContainers[0].command[2]
+          value: |
+            echo 'Trying to reach Gitea on http://my-gitea-svc-http:3210'
+            until timeout 10 wget --no-check-certificate --spider http://my-gitea-svc-http:3210; do
+              sleep 3
+              echo "Trying again in 3 seconds..."
+            done
+            echo "Gitea has been reached!"