FIX: Use SolvedTopics to list posts in /activity/solved instead of user actions (#376)

In https://github.com/discourse/discourse-solved/pull/342 we moved solutions away from topic_custom_fields into proper tables, with the tables as the proper source of truth to a topic's solution.

The user's /my/activity/solved route uses user_actions which is not accurate, and a user has reported a bug where their solution is not reflected there (user actions are not a good representation of what a topic's solution is). 

This commit introduces 
- a new route to get solutions, and is mindful `hide_user_profiles_from_public` and such settings
- also mindful of PMs and private categories
- a new template that makes use of the `<UserStream>` to load posts safely and avoid reimplementation

assets/javascripts/discourse/routes/user-activity-solved.js

@@ -1,15 +1,110 @@
-import UserActivityStreamRoute from "discourse/routes/user-activity-stream";
+import { tracked } from "@glimmer/tracking";
+import EmberObject from "@ember/object";
+import { service } from "@ember/service";
+import { Promise } from "rsvp";
+import { ajax } from "discourse/lib/ajax";
+import DiscourseRoute from "discourse/routes/discourse";
 import { i18n } from "discourse-i18n";
 
-export default class UserActivitySolved extends UserActivityStreamRoute {
-  userActionType = 15;
-  noContentHelpKey = "solved.no_solutions";
+class SolvedPostsStream {
+  @tracked content = [];
+  @tracked loading = false;
+  @tracked loaded = false;
+  @tracked itemsLoaded = 0;
+  @tracked canLoadMore = true;
+
+  constructor({ username, siteCategories }) {
+    this.username = username;
+    this.siteCategories = siteCategories;
+  }
+
+  get noContent() {
+    return this.loaded && this.content.length === 0;
+  }
+
+  findItems() {
+    if (this.loading || !this.canLoadMore) {
+      return Promise.resolve();
+    }
+
+    this.loading = true;
+
+    const limit = 20;
+    return ajax(
+      `/solution/by_user.json?username=${this.username}&offset=${this.itemsLoaded}&limit=${limit}`
+    )
+      .then((result) => {
+        const userSolvedPosts = result.user_solved_posts || [];
+
+        if (userSolvedPosts.length === 0) {
+          this.canLoadMore = false;
+          return;
+        }
+
+        const posts = userSolvedPosts.map((p) => {
+          const post = EmberObject.create(p);
+          post.set("titleHtml", post.topic_title);
+          post.set("postUrl", post.url);
+
+          if (post.category_id && this.siteCategories) {
+            post.set(
+              "category",
+              this.siteCategories.find((c) => c.id === post.category_id)
+            );
+          }
+          return post;
+        });
+
+        this.content = [...this.content, ...posts];
+        this.itemsLoaded = this.itemsLoaded + userSolvedPosts.length;
+
+        if (userSolvedPosts.length < limit) {
+          this.canLoadMore = false;
+        }
+      })
+      .finally(() => {
+        this.loaded = true;
+        this.loading = false;
+      });
+  }
+}
+
+export default class UserActivitySolved extends DiscourseRoute {
+  @service site;
+  @service currentUser;
+
+  model() {
+    const user = this.modelFor("user");
+
+    const stream = new SolvedPostsStream({
+      username: user.username,
+      siteCategories: this.site.categories,
+    });
+
+    return stream.findItems().then(() => {
+      return {
+        stream,
+        emptyState: this.emptyState(),
+      };
+    });
+  }
+
+  setupController(controller, model) {
+    controller.setProperties({
+      model,
+      emptyState: this.emptyState(),
+    });
+  }
+
+  renderTemplate() {
+    this.render("user-activity-solved");
+  }
 
   emptyState() {
     const user = this.modelFor("user");
 
     let title, body;
-    if (this.isCurrentUser(user)) {
+    if (this.currentUser && user.id === this.currentUser.id) {
       title = i18n("solved.no_solved_topics_title");
       body = i18n("solved.no_solved_topics_body");
     } else {

assets/javascripts/discourse/templates/user-activity-solved.gjs

@@ -0,0 +1,16 @@
+import RouteTemplate from "ember-route-template";
+import EmptyState from "discourse/components/empty-state";
+import UserStream from "discourse/components/user-stream";
+
+export default RouteTemplate(
+  <template>
+    {{#if @controller.model.stream.noContent}}
+      <EmptyState
+        @title={{@controller.model.emptyState.title}}
+        @body={{@controller.model.emptyState.body}}
+      />
+    {{else}}
+      <UserStream @stream={{@controller.model.stream}} />
+    {{/if}}
+  </template>
+);