[MM-36995] Start using db native JSON datatypes (#17930)

* Start using db native JSON datatypes

* Fix syntax to work on MySQL 5.7.12

go.mod

@@ -68,7 +68,7 @@ require (
 	github.com/lib/pq v1.10.2
 	github.com/mailru/easyjson v0.7.7 // indirect
 	github.com/mattermost/go-i18n v1.11.0
-	github.com/mattermost/gorp v1.6.2-0.20210419141818-0904a6a388d3
+	github.com/mattermost/gorp v1.6.2-0.20210714143452-8b50f5209a7f
 	github.com/mattermost/gosaml2 v0.3.3
 	github.com/mattermost/gziphandler v0.0.1
 	github.com/mattermost/ldap v0.0.0-20201202150706-ee0e6284187d