feat: improve UX for external configuration (#6861)

* docs: simplify traefik external tls

* remove pass host header

* docs: simplify and fix nginx external tls

* fix: readiness with enabled tls

* improve proxy docs

* improve proxy docs

* fix(ready): don't verify server cert

* complete nginx docs

* cleanup

* complete traefik docs

* add caddy docs

* simplify traefik

* standardize

* fix caddy

* add httpd docs

* improve external config docs

* guiding error message

* docs(defaults.yaml): remove misleading comments

* guiding error message cs and ru

* improve proxy testability

* fix compose up command

* improve commands

* fix nginx tls disabled

* fix nginx tls enabled

* fix: serve gateway when tls is enabled

* fmt caddy files

* fix caddy enabled tls

* remove not-working commands

* review

* fix checks

* fix link

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Co-authored-by: Livio Spring <livio.a@gmail.com>

internal/static/i18n/it.yaml

@@ -318,7 +318,7 @@ Errors:
       NotActive: Grant del progetto non è attivo
       NotInactive: Grant del progetto non è inattivo
   IAM:
-    NotFound: Istanza non trovata
+    NotFound: Istanza non trovata. Controlla https://zitadel.com/docs/self-hosting/manage/custom-domain
     Member:
       RolesNotChanged: I ruoli non sono stati cambiati
     MemberInvalid: Il membro non è valido