feat: enhance openshift support (#1063)

### Description of the change

Add options to values.yaml to make chart easier to install in restricted openshift environments

### Benefits

more people can run this

### Checklist

<!-- [Place an '[X]' (no spaces) in all applicable fields. Please remove unrelated fields.] -->

- [x] Parameters are documented in the `values.yaml` and added to the `README.md` using [readme-generator-for-helm](https://github.com/bitnami-labs/readme-generator-for-helm)
- [ ] Breaking changes are documented in the `README.md`
- [x] Helm templating unittests are added (required when changing anything in `templates` folder)
- [ ] Bash unittests are added (required when changing anything in `scripts` folder)
- [x] All added template resources MUST render a namespace in metadata

---------

Co-authored-by: Lunny Xiao <xiaolunwen@gmail.com>
Reviewed-on: https://gitea.com/gitea/helm-gitea/pulls/1063
Reviewed-by: Lunny Xiao <xiaolunwen@gmail.com>
Co-authored-by: techknowlogick <techknowlogick@gitea.com>
Co-committed-by: techknowlogick <techknowlogick@gitea.com>

unittests/helm/tests/test-http-connection.yaml

@@ -0,0 +1,24 @@
+suite: test connection template
+release:
+  name: gitea-unittests
+  namespace: testing
+templates:
+  - templates/tests/test-http-connection.yaml
+tests:
+  - it: renders openshift-compatible defaults for the test pod
+    set:
+      openshift.enabled: true
+    asserts:
+      - equal:
+          path: spec.hostUsers
+          value: false
+      - equal:
+          path: spec.containers[0].securityContext
+          value:
+            allowPrivilegeEscalation: false
+            capabilities:
+              drop:
+                - ALL
+            runAsNonRoot: true
+            seccompProfile:
+              type: RuntimeDefault