feat(agents): Add Deezer API artist image provider agent (#4180)

* feat(agents): Add Deezer API artist image provider agent

* fix(agents): Use proper naming convention of consts

* fix(agents): Check if json test data can be read

* fix(agents): Use underscores for unused function arguments

* fix(agents): Move int literal to deezerArtistSearchLimit const

* feat: add Deezer configuration option to disable it.

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

---------

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

core/agents/deezer/deezer_suite_test.go

@@ -0,0 +1,17 @@
+package deezer
+
+import (
+	"testing"
+
+	"github.com/navidrome/navidrome/log"
+	"github.com/navidrome/navidrome/tests"
+	. "github.com/onsi/ginkgo/v2"
+	. "github.com/onsi/gomega"
+)
+
+func TestDeezer(t *testing.T) {
+	tests.Init(t, false)
+	log.SetLevel(log.LevelFatal)
+	RegisterFailHandler(Fail)
+	RunSpecs(t, "Deezer Test Suite")
+}