Implement GET channels endpoints for APIv4 (#5363)

* implement get channels endpoints and updated drivers and unittests

* removed channel deletion on tear down, removed manage permission on get channels endpoints, and updated utils to add constant channel length

* added constants for user, team and channel length, updated context to use the model functions

* make sure team name length should be less than the minimum length and revert underscore to team name validity

* changed post test condition from notfound to unauthorized

model/team.go

@@ -22,6 +22,7 @@ const (
 	TEAM_DISPLAY_NAME_MAX_RUNES     = 64
 	TEAM_EMAIL_MAX_LENGTH           = 128
 	TEAM_NAME_MAX_LENGTH            = 64
+	TEAM_NAME_MIN_LENGTH            = 2
 )
 
 type Team struct {
@@ -228,7 +229,7 @@ func IsValidTeamName(s string) bool {
 		return false
 	}
 
-	if len(s) <= 1 {
+	if len(s) < TEAM_NAME_MIN_LENGTH {
 		return false
 	}