OpenAPI: Add namespace into server url?

[bkoelman]

See conversation at microsoft/kiota#4004.

Depends on #1479.

[bkoelman]

Doing so generates broken NSwag/Kiota clients, because the endpoint URL already contains the namespace prefix. When no server URL is emitted, the endpoints in the swagger.json (procured by Swashbuckle) are wrong. This is not a good idea.