Download (and upload) avatar images from mattermost and telegram when mediaserver is configured. Closes #362

An extra avatarMap (cache) is created for mattermost and telegram.
If MediaServerUpload is configured, the avatar images of users are downloaded the first time a
user sends a message.
If this download succeeds a message with EVENT_AVATAR_DOWNLOAD is sent to the originating protocol.
This message also contains a SHA field (in msg.Extra["file"]), if this is not empty, the sha will
be added to the avatarMap. (so we now have a userid-sha cache)

Next time this user sends a message, the MediaServerUpload/sha/userid.png URL will be used as the
avatar field.

1 files changed, 7 insertions, 0 deletions

diff --git a/bridge/helper/helper.go b/bridge/helper/helper.go
index 10c3647a..44052e11 100644
--- a/bridge/helper/helper.go
+++ b/bridge/helper/helper.go
@@ -54,3 +54,10 @@ func HandleExtra(msg *config.Message, general *config.Protocol) []config.Message
 	}
 	return rmsg
 }
+
+func GetAvatar(av map[string]string, userid string, general *config.Protocol) string {
+	if sha, ok := av[userid]; ok {
+		return general.MediaServerUpload + "/" + sha + "/" + userid + ".png"
+	}
+	return ""
+}