actions: Make EventAction complete.

This resolves the long list of type errors Flow saw in eventToAction.

It also resolves an even longer list of type errors in reducers, which
have been hidden by a curious Flow issue; the next commit applies a
workaround for that issue, which exposes all those errors and is how I
found these types were missing from the EventAction union.

As a nice little bonus, it lets us simplify the definition of Action.

src/actionTypes.js

@@ -533,7 +533,27 @@ export type EventReactionAction = EventReactionAddAction | EventReactionRemoveAc
 
 export type EventTypingAction = EventTypingStartAction | EventTypingStopAction;
 
-export type EventAction = EventSubscriptionAction | EventUserAction;
+export type EventAction =
+  | EventAlertWordsAction
+  | EventReactionAddAction
+  | EventReactionRemoveAction
+  | EventNewMessageAction
+  | EventMessageDeleteAction
+  | EventUpdateMessageAction
+  | EventMutedTopicsAction
+  | EventPresenceAction
+  | EventUpdateGlobalNotificationsSettingsAction
+  | EventStreamAction
+  | EventSubscriptionAction
+  | EventTypingAction
+  | EventRealmEmojiUpdateAction
+  | EventRealmFiltersAction
+  | EventUpdateDisplaySettingsAction
+  | EventUpdateMessageFlagsAction
+  | EventUserAction
+  | EventUserGroupAction
+  | {| type: 'ignore' |}
+  | {| type: 'unknown', event: {} |};
 
 export type InitRealmEmojiAction = {|
   type: typeof INIT_REALM_EMOJI,
@@ -619,26 +639,15 @@ type AccountAction =
   | LoginSuccessAction
   | LogoutAction;
 
-type AlertWordsAction = EventAlertWordsAction;
-
 type DraftsAction = DraftUpdateAction;
 
 type LoadingAction = DeadQueueAction | InitialFetchStartAction | InitialFetchCompleteAction;
 
-type MessageAction =
-  | MessageFetchStartAction
-  | MessageFetchCompleteAction
-  | EventReactionAddAction
-  | EventReactionRemoveAction
-  | EventNewMessageAction
-  | EventMessageDeleteAction
-  | EventUpdateMessageAction;
-
-type MuteAction = EventMutedTopicsAction;
+type MessageAction = MessageFetchStartAction | MessageFetchCompleteAction;
 
 type OutboxAction = MessageSendStartAction | MessageSendCompleteAction | DeleteOutboxMessageAction;
 
-type PresenceAction = EventPresenceAction | PresenceResponseAction;
+type PresenceAction = PresenceResponseAction;
 
 type RealmAction =
   | RealmInitAction
@@ -660,29 +669,24 @@ type SessionAction =
   | DebugFlagToggleAction
   | ToggleOutboxSendingAction;
 
-type SettingsAction = SettingsChangeAction | EventUpdateGlobalNotificationsSettingsAction;
+type SettingsAction = SettingsChangeAction;
 
-type StreamAction = InitStreamsAction | EventStreamRemoveAction | EventStreamUpdateAction;
+type StreamAction = InitStreamsAction;
 
-type SubscriptionsAction =
-  | InitSubscriptionsAction
-  | EventSubscriptionAddAction
-  | EventSubscriptionRemoveAction
-  | EventSubscriptionUpdateAction;
+type SubscriptionsAction = InitSubscriptionsAction;
 
 type TopicsAction = InitTopicsAction;
 
-type TypingAction = EventTypingAction | ClearTypingAction;
+type TypingAction = ClearTypingAction;
 
 /** Covers all actions we ever `dispatch`. */
 // The grouping here is completely arbitrary; don't worry about it.
 export type Action =
+  | EventAction
   | AccountAction
-  | AlertWordsAction
   | DraftsAction
   | LoadingAction
   | MessageAction
-  | MuteAction
   | OutboxAction
   | PresenceAction
   | RealmAction

src/events/eventToAction.js

@@ -194,7 +194,7 @@ const updateDisplaySettings = (
   type: EVENT_UPDATE_DISPLAY_SETTINGS,
 });
 
-export default (state: GlobalState, event: Object): $FlowFixMe<EventAction> => {
+export default (state: GlobalState, event: Object): EventAction => {
   switch (event.type) {
     case 'alert_words':
       return alertWords(state, event);