reverseproxy: Add support for specifying IDs in Caddyfile

caddytest/integration/caddyfile_adapt/reverse_proxy_ids.txt

@@ -0,0 +1,46 @@
+:8884
+
+reverse_proxy one|http://localhost two|http://localhost {
+	to three|srv+http://localhost four|srv+http://localhost
+}
+----------
+{
+	"apps": {
+		"http": {
+			"servers": {
+				"srv0": {
+					"listen": [
+						":8884"
+					],
+					"routes": [
+						{
+							"handle": [
+								{
+									"handler": "reverse_proxy",
+									"upstreams": [
+										{
+											"dial": "localhost:80",
+											"id": "one"
+										},
+										{
+											"dial": "localhost:80",
+											"id": "two"
+										},
+										{
+											"id": "three",
+											"lookup_srv": "localhost"
+										},
+										{
+											"id": "four",
+											"lookup_srv": "localhost"
+										}
+									]
+								}
+							]
+						}
+					]
+				}
+			}
+		}
+	}
+}

modules/caddyhttp/reverseproxy/caddyfile.go

@@ -219,6 +219,12 @@ func (h *Handler) UnmarshalCaddyfile(d *caddyfile.Dispenser) error {
 	// treated as a SRV-based upstream, and any port will be
 	// dropped.
 	appendUpstream := func(address string) error {
+		var id string
+		if strings.Contains(address, "|") {
+			parts := strings.SplitN(address, "|", 2)
+			id = parts[0]
+			address = parts[1]
+		}
 		isSRV := strings.HasPrefix(address, "srv+")
 		if isSRV {
 			address = strings.TrimPrefix(address, "srv+")
@@ -231,9 +237,9 @@ func (h *Handler) UnmarshalCaddyfile(d *caddyfile.Dispenser) error {
 			if host, _, err := net.SplitHostPort(dialAddr); err == nil {
 				dialAddr = host
 			}
-			h.Upstreams = append(h.Upstreams, &Upstream{LookupSRV: dialAddr})
+			h.Upstreams = append(h.Upstreams, &Upstream{ID: id, LookupSRV: dialAddr})
 		} else {
-			h.Upstreams = append(h.Upstreams, &Upstream{Dial: dialAddr})
+			h.Upstreams = append(h.Upstreams, &Upstream{ID: id, Dial: dialAddr})
 		}
 		return nil
 	}