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

---------

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

internal/static/i18n/de.yaml

@@ -317,7 +317,7 @@ Errors:
       NotActive: Projekt Grant ist nicht aktiv
       NotInactive: Projekt Grant ist nicht inaktiv
   IAM:
-    NotFound: Instanz nicht gefunden
+    NotFound: Instanz nicht gefunden. Schau dir https://zitadel.com/docs/self-hosting/manage/custom-domain an
     Member:
       RolesNotChanged: Rollen wurden nicht verändert
     MemberInvalid: Member ist ungültig