default ForwardedHeader configutaion

[WeihanLi]

Is there an existing issue for this?

• I have searched the existing issues

Is your feature request related to a problem? Please describe the problem.

When running behind a reverse proxy, we need to use the forwarded headers to get the real request info, currently, we have ASPNETCORE_FORWARDEDHEADERS_ENABLED env config to enable the forwarded headers middleware, but we still need to configure the ForwardedHeadersOptions manually in our code, how about support configure the options from configuration like the ASPNETCORE_FORWARDEDHEADERS_ENABLED env, so that we could configure forwarded header related from configuration only, no need to make updates in code

Describe the solution you'd like

maybe add similar configs like
ASPNETCORE_FORWARDEDHEADERS_Headers/ASPNETCORE_FORWARDEDHEADERS_KnownNetworks/ASPNETCORE_FORWARDEDHEADERS_KnownProxies

Additional context

No response

[WeihanLi]

ForwardedHeadersOptionsSetup has already supported for ASPNETCORE_FORWARDEDHEADERS_ENABLED, there's a test case related:

• aspnetcore/src/DefaultBuilder/test/Microsoft.AspNetCore.Tests/WebHostTests.cs

  Line 58 in 67feeaa

  public async Task WebHostConfiguration_EnablesForwardedHeadersFromConfig()

• https://github.com/dotnet/aspnetcore/blob/main/src/DefaultBuilder/src/WebApplicationBuilder.cs#L38

• aspnetcore/src/Hosting/Hosting/src/GenericHost/WebHostBuilderBase.cs

  Line 23 in 62ece1b

  configBuilder.AddEnvironmentVariables(prefix: "ASPNETCORE_");

• https://github.com/dotnet/runtime/blob/710270696ee9fbbafefacd82423c1fd07b8c3f09/src/libraries/Microsoft.Extensions.Configuration/src/ConfigurationProvider.cs#L24

Since the ForwardedHeaders.Prefix had been supported, we'd like to include the ForwardedHeaders.Prefix support, but seemed for now we had to update our codebase

Should we use ForwardedHeaders.All for the ForwardedHeaders when ForwardedHeaders_Enabled enabled explicitly, like KnownNetworks/KnownProxies? So that we could configure them from configuration without updating the codebase