Add proxying gravatar requests for user avatars (#148)

Fix getting avatar based on email

Remove avatarUrl from user struct

Fix staticcheck

Add default avatar size

Add config option for caching avatars

go mod vendor

Add swagger docs

Add proxying gravatar requests for user avatars

Co-authored-by: kolaente <k@knt.li>
Reviewed-on: https://kolaente.dev/vikunja/api/pulls/148

pkg/routes/api/v1/auth.go

@@ -46,8 +46,6 @@ func NewUserJWTAuthtoken(user *user.User) (token string, err error) {
 	claims["email"] = user.Email
 	claims["exp"] = time.Now().Add(time.Hour * 72).Unix()
 
-	claims["avatar"] = user.AvatarURL
-
 	// Generate encoded token and send it as response.
 	return t.SignedString([]byte(config.ServiceJWTSecret.GetString()))
 }