feat(subsonic): add internet radio support

* Initial commit of internet radio support.

* Added first test for internet radio.

* Refactor to prepare for more test cases.

* Added a few more tests. Realized that I was not calling as admin so added ability to mock admin.

* Added more internet radio tests. Added proper JSON unmarshaling for ID.

* More test cases. Fixed some accidental tabs in files.

* Fixed some more tabs.

* lint fixes

* Changed placeholder for homepage URL to fit into box.

* Finished out internet radio test cases. Found a few bad error codes in internet radio AND podcasts (mea culpa).

* Realized that delete via website was not checking properly if id existed. Fixed.

gofmt

db/model.go

@@ -396,3 +396,14 @@ type Bookmark struct {
 	CreatedAt   time.Time
 	UpdatedAt   time.Time
 }
+
+type InternetRadioStation struct {
+	ID           int `gorm:"primary_key"`
+	StreamURL    string
+  Name         string
+  HomepageURL  string
+}
+
+func (ir *InternetRadioStation) SID() *specid.ID {
+	return &specid.ID{Type: specid.InternetRadioStation, Value: ir.ID}
+}