GeoTIFFSource: Specifying a custom client

[BeGj]

Background:
GeoTIFFSource does not accept any custom client despite geotiff.js supporting this behaviour using the method fromCustomClient (instead of fromUrl).

Proposal:
I propose that when constructing the GeoTIFFSource we allow the developer to specify a custom client.

Example use case:
In Angular it makes it possible to create a client based on Angulars' HttpClient which makes it possible to automatically add a JWT token to the header of each request using the HttpClients HttpInterceptors. This is very usefull when protecting COGs behind a protected reverse-proxy. Instead of manually updating the sources sourceOptions on every token refresh.

Sources:

1. fromCustomClient on https://geotiffjs.github.io/geotiff.js/module-geotiff.html
2. The pull request that enabled it Make it possible to build a RemoteSource with a user-provided client geotiffjs/geotiff.js#370

I would love any feedback on this propoasl, and I'm willing to contribute the code to make it happend. (It's just a few lines of code as I see it. no need to code any clients. Just add the possibility to overwrite with your own).

[ahocevar]

I don't think we'd want to expose GeoTIFF's BaseClient and BaseResponse APIs. But we could accept a function (headers: HeadersInit, abortSignal: AbortSignal): Promise<Response> as url option.

[BeGj]

I don't think we'd want to expose GeoTIFF's BaseClient and BaseResponse APIs. But we could accept a function (headers: HeadersInit, abortSignal: AbortSignal): Promise<Response> as url option.

Thank you, that is a good point which I agree on.