Add renderHtmlPartial function

[kodeFant]

When using respondHtml, rendering partial hsx functions will fail if trying to use fromFrozenContext and related utilities like currentUser.

This makes patching a view with html partials less convenient, for example for htmx users.

With renderHtmlPartial this will work.

[kodeFant]

I noticed an issue with this on a production server, but not in development mode.

I tried to manually run a partial endpoint with a missing required parameter.

This resulted in 502 Bad Gateway and looks like the server panics globally for 2 seconds and also errors globally on the site, then it recovers works fine again.

The expected response should be the IHP error response.

So that seems to be a little risk factor if an attacker would feel like bringing a site down.

I would guess it's the same issue as this one: #1028

[kodeFant]

Here are some error logs from the server:

Oct 10 13:50:42 kompak-prototype RunProdServer[215109]: ParamNotFoundException {name = "framework"}
Oct 10 13:50:42 kompak-prototype nginx[215099]: 2023/10/10 13:50:42 [error] 215099#215099: *22448 upstream prematurely closed connection while reading response header from upstream, client: 84.234.224.78, server: kompak.ai, request: "GET /GetFrameworkHelpTextPartial HTTP/2.0", upstream: "http://127.0.0.1:8000/GetFrameworkHelpTextPartial", host: "kompak.ai"
Oct 10 13:50:42 kompak-prototype nginx[215099]: 2023/10/10 13:50:42 [error] 215099#215099: *22448 connect() failed (111: Connection refused) while connecting to upstream, client: 84.234.224.78, server: kompak.ai, request: "GET /GetFrameworkHelpTextPartial HTTP/2.0", upstream: "http://[::1]:8000/GetFrameworkHelpTextPartial", host: "kompak.ai"

Update: The same happens with respondHtml directly, so then it's likely a more underlying issue