Document authentication mechanisms

[Mathieu Pillard]

Per

iprepd/auth.go

Lines 17 to 34 in cf2290d

 func auth(rf func(http.ResponseWriter, *http.Request)) func(http.ResponseWriter, *http.Request) { 
 	return func(w http.ResponseWriter, r *http.Request) { 
 		if !sruntime.cfg.Auth.DisableAuth { 
 			hdr := r.Header.Get("Authorization") 
 			v := false 
 			if strings.HasPrefix(hdr, "Hawk ") { 
 				v = hawkAuth(r) 
 			} else if strings.HasPrefix(hdr, "APIKey ") { 
 				v = apiAuth(r) 
 			} 
 			if !v { 
 				w.WriteHeader(http.StatusUnauthorized) 
 				return 
 			} 
 		} 
 		rf(w, r) 
 	} 
 } 

iprepd uses Authentication header with either hawk or token auth using Hawk or APIKey prefixes. This should be documented in the README.