[5.3] Allow the substrings 'private-' or 'presence-' within private/presence channel names

[jalipert]

Fixed an issue that prevented authentication in private or presence channels containing the words 'private' or 'presence' in their channel names.

[jalipert]

This issue got me when first trying to implement private broadcasting channels and I happened to name my channel 'test-private-channel' (seemed like a reasonable name at the time). I was unable to authenticate and traced the issue to a global string replace in the channel names.

[taylorotwell]

But you're not replacing the first private-, only presence-... ? This is different from current behavior.

[jalipert]

Yes I am, in lines 46 and 54 in the two files, respectively. Maybe it would be more clear if the second part of my change was in an "else" block?

If the channel name starts with "private-" I'm replacing the first occurrence of "private-". Otherwise, I'm replacing the first occurrence of "presence-". Due to the preceding section, we already know that it starts with one of those strings. And as far as I know, there's no clear way to replace one or the other in a one-liner.