Tests should test all legal server name formats

Nobody has claimed this yet.

I ran into an issue with generic hooks when running Hookshot on localhost with the server name set to `localhost:8448`.

```log
INFO 12:16:27:794 [GenericHookConnection] onGenericHook !QrmxBsBKPajykCohPz:localhost:8448 7e789bf2-7b87-4b10-9438-a22a6f1090d2
ERROR 12:16:27:800 [Appservice] Error registering user: User ID is in use
ERROR 12:16:27:804 [MatrixHttpClient] (REQ-15) {
errcode: 'M_FORBIDDEN',
error: 'Application service cannot masquerade as this user (@_webhooks_hookname:localhost).'
}
WARN 12:16:27:804 [Bridge] Failed to handle generic webhook MatrixError: M_FORBIDDEN: Application service cannot masquerade as this user (@_webhooks_hookname:localhost).
at Object.defaultErrorHandler [as errorHandler] (/usr/bin/matrix-hookshot/node_modules/matrix-bot-sdk/lib/http.js:10:9)
at doHttpRequest (/usr/bin/matrix-hookshot/node_modules/matrix-bot-sdk/lib/http.js:98:31)
at process.processTicksAndRejections (node:internal/process/task_queues:105:5)
at async descriptor.value (/usr/bin/matrix-hookshot/node_modules/matrix-bot-sdk/lib/metrics/decorators.js:19:32)
at async descriptor.value (/usr/bin/matrix-hookshot/node_modules/matrix-bot-sdk/lib/metrics/decorators.js:19:32)
at async GenericHookConnection.ensureDisplayname (/usr/bin/matrix-hookshot/Connections/GenericHook.js:271:13)
at async GenericHookConnection.onGenericHook (/usr/bin/matrix-hookshot/Connections/GenericHook.js:478:13)
at async /usr/bin/matrix-hookshot/Bridge.js:435:25
at async Promise.all (index 0)
at async LocalMQ. (/usr/bin/matrix-hookshot/Bridge.js:410:13) {
body: {
errcode: 'M_FORBIDDEN',
error: 'Application service cannot masquerade as this user (@_webhooks_hookname:localhost).'
},
statusCode: 403,
errcode: 'M_FORBIDDEN',
error: 'Application service cannot masquerade as this user (@_webhooks_hookname:localhost).',
retryAfterMs: undefined
}
```

I proposed a fix to this specific bug in https://github.com/matrix-org/matrix-hookshot/pull/999, but would be nice if tests checked this for all Hookshot features.

Having the port in the server name is legal according to the Spec: https://spec.matrix.org/v1.12/appendices/#server-name

Start by reviewing the generic-hook path identified in the report, including Connections/GenericHook.js, and compare it with proposed fix PR #999. Locate the existing tests for Hookshot features and extend coverage to legal Matrix server-name formats, including localhost:8448; done means all relevant features accept the formats without producing an invalid user ID.

Written by the indexing model from the issue text.