Refactor reverse proxy and enhance API routing

- Replaced the existing reverse proxy implementation with a new alias forwarding mechanism, improving path handling and request normalization.
- Updated the gateway to utilize the new forwarding approach, ensuring consistent handling of API requests and proper error management.
- Enhanced tests to validate the new routing behavior, including handling of double slashes and user endpoint requests.
- Improved documentation in GATEWAY_RUN.md to clarify the updated API routing and configuration requirements.

internal/proxy/reverse.go

@@ -2,8 +2,6 @@ package proxy
 
 import (
 	"net/http"
-	"net/http/httputil"
-	"net/url"
 	"path"
 	"strings"
 )
@@ -11,7 +9,7 @@ import (
 // NormalizeRequestURLPath collapses duplicate slashes and dot-segments in req.URL.Path
 // (path.Clean) and clears RawPath so strip-prefix routing matches the client path even
 // when the request line contained "//" (e.g. /api//mtg/health). Without this, the path
-// may not match /api/{alias} and SingleHostReverseProxy forwards a wrong path upstream.
+// may not match /api/{alias} and alias routing fails.
 func NormalizeRequestURLPath(req *http.Request) {
 	if req == nil || req.URL == nil {
 		return
@@ -29,78 +27,3 @@ func NormalizeRequestURLPath(req *http.Request) {
 	u.Path = c
 	u.RawPath = ""
 }
-
-// NewReverseProxy builds a reverse proxy to target base URL with path rewriting:
-// stripPrefix (/api/{alias}) + pathPrefix (/v1) + remainder, joined onto target via url.JoinPath
-// (e.g. https://host/api/ + v1 + health → https://host/v1/health).
-//
-// Compatibility: GET/HEAD .../api/{alias}/users (list only, no extra path segment) is sent upstream as
-// /v1/stats/users. Some Telemt builds treat GET /v1/users incorrectly (e.g. 400) while /v1/stats/users works.
-// POST .../users (create) and GET .../users/{username} are unchanged.
-func NewReverseProxy(target *url.URL, stripPrefix, pathPrefix string, setAuth string) *httputil.ReverseProxy {
-	proxy := httputil.NewSingleHostReverseProxy(target)
-	proxy.Transport = DirectTransport()
-	orig := proxy.Director
-	targetQuery := target.RawQuery
-	proxy.Director = func(req *http.Request) {
-		NormalizeRequestURLPath(req)
-		p := req.URL.Path
-		if !strings.HasPrefix(p, stripPrefix) {
-			orig(req)
-			if setAuth != "" {
-				req.Header.Set("Authorization", setAuth)
-			}
-			// Server-side requests carry RequestURI; client RoundTrip rejects it with URL.Host set.
-			req.RequestURI = ""
-			req.Header.Del("Host")
-			req.Host = req.URL.Host
-			return
-		}
-		rest := strings.TrimPrefix(p, stripPrefix)
-		rest = strings.TrimPrefix(rest, "/")
-		if (req.Method == http.MethodGet || req.Method == http.MethodHead) && rest == "users" {
-			rest = "stats/users"
-		}
-		joined := buildUpstreamURL(target, pathPrefix, rest)
-		req.URL.Scheme = joined.Scheme
-		req.URL.Host = joined.Host
-		req.URL.Path = joined.Path
-		req.URL.RawPath = joined.RawPath
-		req.URL.Opaque = ""
-		// Match Host header to authority; clear stale map entry (e.g. from httptest.NewRequest).
-		req.Header.Del("Host")
-		req.Host = req.URL.Host
-		if targetQuery == "" || req.URL.RawQuery == "" {
-			req.URL.RawQuery = targetQuery + req.URL.RawQuery
-		} else {
-			req.URL.RawQuery = targetQuery + "&" + req.URL.RawQuery
-		}
-		if setAuth != "" {
-			req.Header.Set("Authorization", setAuth)
-		}
-		req.RequestURI = ""
-	}
-	return proxy
-}
-
-func buildUpstreamURL(target *url.URL, pathPrefix, rest string) *url.URL {
-	rel := strings.Trim(pathPrefix, "/")
-	if rest != "" {
-		if rel != "" {
-			rel = rel + "/" + rest
-		} else {
-			rel = rest
-		}
-	}
-	var parts []string
-	for _, seg := range strings.Split(rel, "/") {
-		if seg != "" {
-			parts = append(parts, seg)
-		}
-	}
-	if len(parts) == 0 {
-		out := *target
-		return &out
-	}
-	return target.JoinPath(parts...)
-}