MODAL: Untangle `onSelectPanel`

Previously modal-tab component would call on click the onSelectPanel callback with itself (modal-tab) as `this` which severely limited its usefulness. Now showModal binds the callback to its controller.

app/assets/javascripts/discourse/app/components/modal-tab.js

@@ -20,6 +20,10 @@ export default Component.extend({
   },
 
   click() {
-    this.onSelectPanel(this.panel);
+    this.set("selectedPanel", this.panel);
+
+    if (this.onSelectPanel) {
+      this.onSelectPanel(this.panel);
+    }
   }
 });

app/assets/javascripts/discourse/app/lib/show-modal.js

@@ -50,7 +50,10 @@ export default function(name, opts) {
     });
 
     if (controller.actions.onSelectPanel) {
-      modalController.set("onSelectPanel", controller.actions.onSelectPanel);
+      modalController.set(
+        "onSelectPanel",
+        controller.actions.onSelectPanel.bind(controller)
+      );
     }
 
     modalController.set(

app/assets/javascripts/discourse/app/mixins/modal-functionality.js

@@ -18,10 +18,6 @@ export default Mixin.create({
     closeModal() {
       this.modal.send("closeModal");
       this.set("panels", []);
-    },
-
-    onSelectPanel(panel) {
-      this.set("selectedPanel", panel);
     }
   }
 });