MM-24674 Update channel members by group to look at distinct timezones correctly (#14673)

* MM-24674 Update channel members by group to look at distinct autoTimezone and manualTimezone.

Instead of just doing a blanket distinct on the column since that returns more entries than expected

* Use JSON extract instead of parsing text

* Use single quotes in mysql query too

* Dont need to prepend users on unambiguous column

* Use json extract instead of shorthand

* Dont count timezone if timezone default length

* CI

Co-authored-by: mattermod <mattermod@users.noreply.github.com>

store/sqlstore/channel_store.go

@@ -1811,7 +1811,27 @@ func (s SqlChannelStore) GetMemberCountsByGroup(channelID string, includeTimezon
 	selectStr := "GroupMembers.GroupId, COUNT(ChannelMembers.UserId) AS ChannelMemberCount"
 
 	if includeTimezones {
-		selectStr = "GroupMembers.GroupId, COUNT(ChannelMembers.UserId) AS ChannelMemberCount, COUNT( DISTINCT Users.Timezone ) AS ChannelMemberTimezonesCount"
+		distinctTimezones := `
+			DISTINCT(
+				CASE WHEN JSON_EXTRACT(Timezone, '$.useAutomaticTimezone') = 'true' AND LENGTH(Timezone) > 74
+				THEN JSON_EXTRACT(Timezone, '$.automaticTimezone')
+				WHEN LENGTH(Timezone) > 74
+				THEN JSON_EXTRACT(Timezone, '$.manualTimezone')
+				END
+			)
+		`
+		if s.DriverName() == model.DATABASE_DRIVER_POSTGRES {
+			distinctTimezones = `
+				DISTINCT(
+					CASE WHEN Timezone::json->>'useAutomaticTimezone' = 'true' AND LENGTH(Timezone) > 74
+					THEN Timezone::json->>'automaticTimezone'
+					WHEN LENGTH(Timezone) > 74
+					THEN Timezone::json->>'manualTimezone'
+					END
+				)
+			`
+		}
+		selectStr = `GroupMembers.GroupId, COUNT(ChannelMembers.UserId) AS ChannelMemberCount, COUNT(` + distinctTimezones + `) AS ChannelMemberTimezonesCount`
 	}
 
 	query := s.getQueryBuilder().