URL Host agnostic cache key

[yringler]

We host a lot of (nonprofit) sites on different domains (from the save servers), and want all of them to cache images to the same place, even though the domain is different.
There is at least one workaround.
The first relies on an implementation detail

ImageSharp.Web/src/ImageSharp.Web/Middleware/ImageSharpMiddleware.cs

Line 497 in 451da15

var sb = new StringBuilder(context.Request.Host.ToString());

I suspect there are other ways to get the host / full URL with host? If there are, it's a brittle work around.
The second is better? But it disturbs my aesthetic sense to have ImageSharp carefully create a URI string, just for me to parse it and clumsily remove the host.

Do you think that there should be something added to more gracefully support this?
Maybe add another method to the interface which takes an HttpRequest instead of a string? It could have a default implementation which creates the string as in the line quoted above.

Or a new ImageSharpMiddlewareOptions.IgnoreHost option?

With middleware:

app.Use(async (context, next) =>
{
  context.Request.Host = new Microsoft.AspNetCore.Http.HostString("ourmainhost.org");
  await next();
});
app.UseImageSharp();
app.UseStaticFiles();

And by making a custom ICacheHash
EDIT: This doesn't work, because the string isn't a full URI

using Microsoft.Extensions.Options;
using SixLabors.ImageSharp.Web.Caching;
using SixLabors.ImageSharp.Web.Middleware;
using System;

namespace ImageProcessor
{
	public class HostAgnosticCacheHash : ICacheHash
	{
		private readonly CacheHash cacheHash;

		public HostAgnosticCacheHash(IOptions<ImageSharpMiddlewareOptions> options)
		{
			cacheHash = new CacheHash(options);
		}

		public string Create(string value, uint length)
		{
			var sanatizedUri = new Uri(value);
			
			return cacheHash.Create(value.Replace(sanatizedUri.Host, ""), length);
		}
	}
}

[JimBobSquarePants]

ImageSharpMiddlewareOptions.IgnoreHost

That's the best option. Happy to help if you want to open a PR.

[yringler]

Ok, great! I'll open a PR shortly

[JimBobSquarePants]

Awesome!

[yringler]

Opened #147