Further improvement on DRY principle support (#529)

### Description of the change

- Adding TPL use into './templates/_helpers.tpl' in "gitea.inline_configuration.defaults.server" since '.Values.ingress.hosts' referred

### Benefits

- Avoid error in deployment using Gitea CHart 9.5.0 such as "Invalid ROOT_URL 'https://{{ .Values.global.giteaHostName }}': parse "https://{{ .Values.global.giteaHostName }}": invalid character "{" in host name"

### Possible drawbacks

N/A

### Applicable issues

 - fixes #530

### Checklist

- [x] Fixing './templates/_helpers.tpl' "gitea.inline_configuration.defaults.server
- [x] Templating unittests are added

Co-authored-by: pat-s <pat-s@noreply.gitea.com>
Co-authored-by: justusbunsi <justusbunsi@noreply.gitea.com>
Co-authored-by: 212597596 <cedric.henry@ge.com>
Reviewed-on: https://gitea.com/gitea/helm-chart/pulls/529
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>

templates/_helpers.tpl

@@ -319,7 +319,7 @@ https
   {{- end -}}
   {{- if not (.Values.gitea.config.server.DOMAIN) -}}
     {{- if gt (len .Values.ingress.hosts) 0 -}}
-      {{- $_ := set .Values.gitea.config.server "DOMAIN" (index .Values.ingress.hosts 0).host -}}
+      {{- $_ := set .Values.gitea.config.server "DOMAIN" ( tpl (index .Values.ingress.hosts 0).host $) -}}
     {{- else -}}
       {{- $_ := set .Values.gitea.config.server "DOMAIN" (include "gitea.default_domain" .) -}}
     {{- end -}}