Support custom BaseURL in Opsgenie integration for JSM Operations

The current Opsgenie integration only supports a region selector (US/EU). Replacing or extending this with a configurable baseURL enables support for both standard Opsgenie and Jira Service Management (JSM) Operations.

Given that Opsgenie is approaching End of Life (EOL) and migrating toward JSM Operations, allowing a flexible baseURL ensures seamless support for both services