[XYZ-6] Add sampledata platform command (#8027)

* Add fake dependency

* [XYZ-6] Add sampledata platform command

* Creating EMOJI_NAME_MAX_LENGTH as a constant and using it where needed

glide.yaml

@@ -94,3 +94,4 @@ import:
 - package: gopkg.in/gomail.v2
   version: 2.0.0
 - package: github.com/mattermost/html2text
+- package: github.com/icrowley/fake