MM-55295: Improve DB performance of some (Take 2) (#25865)

* Revert "Revert "MM-55295: Improve DB performance of some APIs (#25318)" (#25852)"

This reverts commit 077221a940.

* Fix the issue

```release-note
NONE
```

* lint fix

```release-note
NONE
```

server/channels/app/authorization.go

@@ -83,7 +83,6 @@ func (a *App) SessionHasPermissionToChannel(c request.CTX, session model.Session
 	}
 
 	ids, err := a.Srv().Store().Channel().GetAllChannelMembersForUser(session.UserId, true, true)
-
 	var channelRoles []string
 	if err == nil {
 		if roles, ok := ids[channelID]; ok {
@@ -260,17 +259,22 @@ func (a *App) HasPermissionToChannel(c request.CTX, askingUserId string, channel
 		return false
 	}
 
-	channelMember, err := a.GetChannelMember(c, channelID, askingUserId)
+	// We call GetAllChannelMembersForUser instead of just getting
+	// a single member from the DB, because it's cache backed
+	// and this is a very frequent call.
+	ids, err := a.Srv().Store().Channel().GetAllChannelMembersForUser(askingUserId, true, true)
+	var channelRoles []string
 	if err == nil {
-		roles := channelMember.GetRoles()
-		if a.RolesGrantPermission(roles, permission.Id) {
-			return true
+		if roles, ok := ids[channelID]; ok {
+			channelRoles = strings.Fields(roles)
+			if a.RolesGrantPermission(channelRoles, permission.Id) {
+				return true
+			}
 		}
 	}
 
-	var channel *model.Channel
-	channel, err = a.GetChannel(c, channelID)
-	if err == nil {
+	channel, appErr := a.GetChannel(c, channelID)
+	if appErr == nil {
 		return a.HasPermissionToTeam(c, askingUserId, channel.TeamId, permission)
 	}