Adding support for hosting with URL prefix

[flowkclav]

Closes #163. Adding support for hosting with URL prefix to make reverse-proxy setup on sub-path possible.

Starting silverbullet server specifying a "prefix" (or "context root") in environment variable SB_URL_PREFIX will cause the application to be hosted on the specified prefix. This allows sub-path configuration when setting up reverse proxies (e.g. https://myserver/sb/ -> http://localhost:3000/sb/ )

Summary of changes:

• server:
  • Hono configured to serve on the prefix, if specified
  • Prefix is removed from incoming URLs in server endpoints for the application to function normally
  • Prefix is added to outgoing redirects
  • Prefix is set as path in authentication cookies
  • Injection of the prefix in the base element of index.html and auth.html
• client:
  • Switching from "absolute" URLs (i.e. host-relative, e.g. /myresource) to page-relative URLs (e.g. myresource)
  • Using document.baseURI instead of location.origin|host when constructing URLs

NOTES:

• Running the formatter modified a file I did not otherwise touch, I did not include it in this PR.
• Likewise, the test I added and modified pass but another test is failing, at least on my setup (JSON utils => ./plug-api/lib/json.test.ts:4:6 fails with Actual 2023-05-02 / Expected 2023-05-03. Probably a timezone thing). I left it alone.

[zefhemel]

Thanks for this. I need the time to properly tests this. I anticipate a lot of edge cases and places where being hosted at the root is implicitly assumed.

[flowkclav]

Absolutely! I am fairly new to silverbullet so it is very possible that I missed something. As if to illustrate my point, I just realised I never tested in offline mode. I just did and sure enough, the service_worker.ts will need tweaking. And unlike the rest of the client code, it doesn't have access to document.baseURI to derive the prefix. I'll try to take a closer if I have some more time.