chore: Allow admins to choose the agent bot from the UI (#5895)

app/javascript/dashboard/api/inboxes.js

@@ -13,6 +13,16 @@ class Inboxes extends ApiClient {
   deleteInboxAvatar(inboxId) {
     return axios.delete(`${this.url}/${inboxId}/avatar`);
   }
+
+  getAgentBot(inboxId) {
+    return axios.get(`${this.url}/${inboxId}/agent_bot`);
+  }
+
+  setAgentBot(inboxId, botId) {
+    return axios.post(`${this.url}/${inboxId}/set_agent_bot`, {
+      agent_bot: botId,
+    });
+  }
 }
 
 export default new Inboxes();