refactor: Move pm_conversations.process_message.

I lift this function out of message_store to
break some dependencies, and it's also more
consistent with the rest of the codebase:

    alert_words.process_message
    pm_conversations.process_message
    recent_topics.process_messages
    recent_senders.process_message_for_senders

We can do further cleanup to make these names
consistent (and possibly have them all work in
bulk), but that's out of the scope of the current PR.

frontend_tests/node_tests/message_store.js

@@ -233,7 +233,7 @@ test("errors", () => {
         "set_partner",
         () => assert(false),
         () => {
-            message_store.process_message_for_recent_private_messages(message);
+            pm_conversations.process_message(message);
         },
     );
 });

static/js/message_helper.js

@@ -2,6 +2,7 @@ import * as alert_words from "./alert_words";
 import * as message_store from "./message_store";
 import * as message_user_ids from "./message_user_ids";
 import * as people from "./people";
+import * as pm_conversations from "./pm_conversations";
 import * as recent_senders from "./recent_senders";
 import * as stream_topic_history from "./stream_topic_history";
 import * as util from "./util";
@@ -59,7 +60,7 @@ export function process_new_message(message) {
             message.pm_with_url = people.pm_with_url(message);
             message.to_user_ids = people.pm_reply_user_string(message);
 
-            message_store.process_message_for_recent_private_messages(message);
+            pm_conversations.process_message(message);
 
             if (people.is_my_user_id(message.sender_id)) {
                 for (const recip of message.display_recipient) {

static/js/message_store.js

@@ -1,7 +1,6 @@
 import * as blueslip from "./blueslip";
 import * as message_list from "./message_list";
 import * as people from "./people";
-import * as pm_conversations from "./pm_conversations";
 
 const stored_messages = new Map();
 
@@ -69,19 +68,6 @@ export function get_pm_full_names(message) {
     return names.join(", ");
 }
 
-export function process_message_for_recent_private_messages(message) {
-    const user_ids = people.pm_with_user_ids(message);
-    if (!user_ids) {
-        return;
-    }
-
-    for (const user_id of user_ids) {
-        pm_conversations.set_partner(user_id);
-    }
-
-    pm_conversations.recent.insert(user_ids, message.id);
-}
-
 export function set_message_booleans(message) {
     const flags = message.flags || [];
 

static/js/pm_conversations.js

@@ -77,6 +77,19 @@ class RecentPrivateMessages {
 
 export let recent = new RecentPrivateMessages();
 
+export function process_message(message) {
+    const user_ids = people.pm_with_user_ids(message);
+    if (!user_ids) {
+        return;
+    }
+
+    for (const user_id of user_ids) {
+        set_partner(user_id);
+    }
+
+    recent.insert(user_ids, message.id);
+}
+
 export function clear_for_testing() {
     recent = new RecentPrivateMessages();
     partners.clear();