fix hub bugs, add channel role permission endpoints

Covers: snake_case param renames, mutex RLock/Unlock mismatches, user.Hubs keyed by hub.Id, hub color using new_name, DELETE params sent as query, delete(target.Hubs, hub.Id), root/member role Id swap, and the three new PATCH
  /hub/channel/roles/* handlers.

packages/httpRequest/get.go

@@ -73,9 +73,9 @@ func getHubUserIfValidWithResponseOnFail(ctx context.Context, response http.Resp
 		return nil, nil, nil, errors.New("invalid token")
 	}
 
-	hub, err := getHubByIdStr(ctx, request.Header.Get("hubid"))
+	hub, err := getHubByIdStr(ctx, request.Header.Get("hub_id"))
 	if err != nil {
-		http.Error(response, "invalid hubid", http.StatusBadRequest)
+		http.Error(response, "invalid hub_id", http.StatusBadRequest)
 		return nil, nil, nil, errors.New("no such hub")
 	}
 
@@ -83,8 +83,8 @@ func getHubUserIfValidWithResponseOnFail(ctx context.Context, response http.Resp
 	hubUser, ok := hub.Users[user.Id]
 	hub.Mu.RUnlock()
 	if !ok {
-		http.Error(response, "invalid hubid", http.StatusUnauthorized)
-		return nil, nil, nil, errors.New("invalid hubid")
+		http.Error(response, "invalid hub_id", http.StatusUnauthorized)
+		return nil, nil, nil, errors.New("invalid hub_id")
 	}
 
 	return user, hubUser, hub, nil
@@ -94,13 +94,16 @@ func getHubChannelIfValidWithResponseOnFail(ctx context.Context, response http.R
 	*types.HubChannel, error) {
 	channelUuid, err := convertions.StringToUuid(channelId)
 	if err != nil {
-		http.Error(response, "invalid channelid", http.StatusBadRequest)
-		return nil, errors.New("invalid channelid")
+		http.Error(response, "invalid channel_id", http.StatusBadRequest)
+		return nil, errors.New("invalid channel_id")
 	}
+
+	hub.Mu.RLock()
 	channel, ok := hub.Channels[channelUuid]
+	hub.Mu.RUnlock()
 	if !ok {
-		http.Error(response, "invalid channelid", http.StatusBadRequest)
-		return nil, errors.New("invalid channelid")
+		http.Error(response, "channel not found", http.StatusNotFound)
+		return nil, errors.New("channel not found")
 	}
 
 	if !haveHubUserCachedPermissions(types.CachedUserCanView, hubUser, channel) {