fix(metrics): write system metrics on start (#3641)

* fix(metrics): write system metrics on start

* add broken basic auth test

* refactor: simplify Prometheus instantiation

Signed-off-by: Deluan <deluan@navidrome.org>

* fix: basic authentication

Signed-off-by: Deluan <deluan@navidrome.org>

* refactor: move magic strings to constants

Signed-off-by: Deluan <deluan@navidrome.org>

* refactor: simplify prometheus http handler

Signed-off-by: Deluan <deluan@navidrome.org>

* add artist metadata to aggregrate sql

---------

Signed-off-by: Deluan <deluan@navidrome.org>
Co-authored-by: Deluan <deluan@navidrome.org>

server/auth_test.go

@@ -219,18 +219,36 @@ var _ = Describe("Auth", func() {
 		})
 	})
 
-	Describe("authHeaderMapper", func() {
-		It("maps the custom header to Authorization header", func() {
-			r := httptest.NewRequest("GET", "/index.html", nil)
-			r.Header.Set(consts.UIAuthorizationHeader, "test authorization bearer")
-			w := httptest.NewRecorder()
+	Describe("tokenFromHeader", func() {
+		It("returns the token when the Authorization header is set correctly", func() {
+			req := httptest.NewRequest("GET", "/", nil)
+			req.Header.Set(consts.UIAuthorizationHeader, "Bearer testtoken")
 
-			authHeaderMapper(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
-				Expect(r.Header.Get("Authorization")).To(Equal("test authorization bearer"))
-				w.WriteHeader(200)
-			})).ServeHTTP(w, r)
+			token := tokenFromHeader(req)
+			Expect(token).To(Equal("testtoken"))
+		})
 
-			Expect(w.Code).To(Equal(200))
+		It("returns an empty string when the Authorization header is not set", func() {
+			req := httptest.NewRequest("GET", "/", nil)
+
+			token := tokenFromHeader(req)
+			Expect(token).To(BeEmpty())
+		})
+
+		It("returns an empty string when the Authorization header is not a Bearer token", func() {
+			req := httptest.NewRequest("GET", "/", nil)
+			req.Header.Set(consts.UIAuthorizationHeader, "Basic testtoken")
+
+			token := tokenFromHeader(req)
+			Expect(token).To(BeEmpty())
+		})
+
+		It("returns an empty string when the Bearer token is too short", func() {
+			req := httptest.NewRequest("GET", "/", nil)
+			req.Header.Set(consts.UIAuthorizationHeader, "Bearer")
+
+			token := tokenFromHeader(req)
+			Expect(token).To(BeEmpty())
 		})
 	})