[NET-4897] net/http host header is now verified and request.host that contains socked now error (#18129)

### Description

This is related to https://github.com/hashicorp/consul/pull/18124 where
we pinned the go versions in CI to 1.20.5 and 1.19.10.

go 1.20.6 and 1.19.11 now validate request host headers for validity,
including the hostname cannot be prefixed with slashes.

For local communications (npipe://, unix://), the hostname is not used,
but we need valid and meaningful hostname. Prior versions go Go would
clean the host header, and strip slashes in the process, but go1.20.6
and go1.19.11 no longer do, and reject the host header. Around the
community we are seeing that others are intercepting the req.host and if
it starts with a slash or ends with .sock, they changing the host to
localhost or another dummy value.

[client: define a "dummy" hostname to use for local connections by
thaJeztah · Pull Request #45942 ·
moby/moby](https://github.com/moby/moby/pull/45942)

### Testing & Reproduction steps

Check CI tests.

### Links
* [ ] updated test coverage
* [ ] external facing docs updated
* [ ] appropriate backport labels added
* [ ] not a security concern

.github/workflows/go-tests.yml

@@ -376,7 +376,7 @@ jobs:
       runs-on: ${{ needs.setup.outputs.compute-xl }}
       repository-name: ${{ github.repository }}
       go-tags: "${{ github.event.repository.name == 'consul-enterprise' && 'consulent consulprem consuldev' || '' }}"
-      go-version: "1.19.10"
+      go-version: "1.19"
     permissions:
       id-token: write # NOTE: this permission is explicitly required for Vault auth.
       contents: read
@@ -395,12 +395,7 @@ jobs:
       runs-on: ${{ needs.setup.outputs.compute-xl }}
       repository-name: ${{ github.repository }}
       go-tags: "${{ github.event.repository.name == 'consul-enterprise' && 'consulent consulprem consuldev' || '' }}"
-      # pinning this to 1.20.5 because this issue in go-testcontainers occurs
-      # in 1.20.6 with the error "http: invalid Host header, host port waiting failed"
-      # https://github.com/testcontainers/testcontainers-go/issues/1359
-      # remove setting this when the above issue is fixed so that the reusable
-      # job will just get the go version from go.mod.
-      go-version: "1.20.5"
+      go-version: "1.20"
     permissions:
       id-token: write # NOTE: this permission is explicitly required for Vault auth.
       contents: read
@@ -438,6 +433,7 @@ jobs:
       runs-on: ${{ needs.setup.outputs.compute-xl }}
       repository-name: ${{ github.repository }}
       go-tags: "${{ github.event.repository.name == 'consul-enterprise' && 'consulent consulprem consuldev' || '' }}"
+      go-version: "1.20"
     permissions:
       id-token: write # NOTE: this permission is explicitly required for Vault auth.
       contents: read

api/api.go

@@ -1000,6 +1000,17 @@ func (r *request) toHTTP() (*http.Request, error) {
 		return nil, err
 	}
 
+	// validate that socket communications that do not use the host, detect
+	// slashes in the host name and replace it with local host.
+	// this is required since go started validating req.host in 1.20.6 and 1.19.11.
+	// prior to that they would strip out the slashes for you.  They removed that
+	// behavior and added more strict validation as part of a CVE.
+	// https://github.com/golang/go/issues/60374
+	// the hope is that
+	if strings.HasPrefix(r.url.Host, "/") {
+		r.url.Host = "localhost"
+	}
+
 	req.URL.Host = r.url.Host
 	req.URL.Scheme = r.url.Scheme
 	req.Host = r.url.Host