Serve postgres's consumers the port its server is published on, not the container's 5432 (issue 957)

On novox postgres is published 6852:5432; handed 5432, gitea and keycloak reached
nothing once their files were filled from postgres's entry.

modules/postgres/cmd/postgres-provider/client.go

@@ -122,6 +122,38 @@ func NewClient(conn Conn, dial Dialer) *Client {
 
 var unfilled = regexp.MustCompile(`^\$\{[^}]*\}$`)
 
+// portFromEnv is the port postgres's server is published on, on its machine: MESH_POSTGRES_PORT, else
+// MESH_PROVISION_POSTGRES_PORT, the seat's twin (mesh-controller's internal/envfile.Placed pattern: which port
+// this machine actually put mesh-store at, when that differs from the connection string's; empty, or a
+// placeholder the mesh never filled, adds nothing), else the connection string's port, else 5432. It is both
+// the port this code reaches the server on and the port its consumers are served (issue 957).
+func portFromEnv(env func(string) string, u *url.URL) int {
+	seatPort := strings.TrimSpace(env("MESH_PROVISION_POSTGRES_PORT"))
+	if unfilled.MatchString(seatPort) {
+		seatPort = ""
+	}
+	portSource := firstOf(env("MESH_POSTGRES_PORT"), seatPort)
+	if portSource == "" && u != nil {
+		portSource = u.Port()
+	}
+	port, err := strconv.Atoi(portSource)
+	if err != nil || port == 0 {
+		return 5432
+	}
+	return port
+}
+
+// publishedPort is portFromEnv read from the environment alone, its connection string parsed here.
+func publishedPort(env func(string) string) int {
+	var u *url.URL
+	if raw := env("MESH_PROVISION_POSTGRES"); raw != "" {
+		if parsed, err := url.Parse(raw); err == nil {
+			u = parsed
+		}
+	}
+	return portFromEnv(env, u)
+}
+
 // ClientFromEnv builds the client from the module's words. MESH_POSTGRES_* first (the documented
 // names), then the MESH_PROVISION_* keys the manifest sets. Fails without a host and an admin password.
 func ClientFromEnv(env func(string) string) (*Client, error) {
@@ -135,21 +167,7 @@ func ClientFromEnv(env func(string) string) (*Client, error) {
 	if host == "" && u != nil {
 		host = u.Hostname()
 	}
-	// MESH_PROVISION_POSTGRES_PORT is the seat's twin (mesh-controller's internal/envfile.Placed
-	// pattern): which port this machine actually put mesh-store at, when that differs from the
-	// connection string's. Empty, or a placeholder the mesh never filled, adds nothing.
-	seatPort := strings.TrimSpace(env("MESH_PROVISION_POSTGRES_PORT"))
-	if unfilled.MatchString(seatPort) {
-		seatPort = ""
-	}
-	portSource := firstOf(env("MESH_POSTGRES_PORT"), seatPort)
-	if portSource == "" && u != nil {
-		portSource = u.Port()
-	}
-	port, err := strconv.Atoi(portSource)
-	if err != nil || port == 0 {
-		port = 5432
-	}
+	port := portFromEnv(env, u)
 	user := env("MESH_POSTGRES_USER")
 	if user == "" && u != nil && u.User != nil {
 		user = u.User.Username()