[discussion] Consider making the const public

[Anant Prakash]

gomatrixserverlib/eventauth.go

Lines 29 to 33 in 9f1b58c

 join   = "join" 
 ban    = "ban" 
 leave  = "leave" 
 invite = "invite" 
 public = "public" 

Since go encourages us not to repeat constant string literals, we should make these public and reference them wherever needed.

[Andrew Morgan]

So just gomatrixserverlib.Join? That's seems fine.