[2.3.0] Checkmk Werk 16898 created: active_checks:httpv2: support macros in 'user_agent' field

[//]: # (werk v2) # active_checks:httpv2: support macros in 'user_agent' field key | value ---------- | --- date | 2024-10-08T11:32:55+00:00 version | 2.3.0p19 class | feature edition | cre component | checks level | 1 compatible | yes While the `endpoint.url` element in httpv2 active check configuration support macro replacement, `user_agent` doesn't. This change adds support for macro replacement also for the `user_agent` field.