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();

app/javascript/dashboard/api/specs/inboxes.spec.js

@@ -11,6 +11,8 @@ describe('#InboxesAPI', () => {
     expect(inboxesAPI).toHaveProperty('update');
     expect(inboxesAPI).toHaveProperty('delete');
     expect(inboxesAPI).toHaveProperty('getCampaigns');
+    expect(inboxesAPI).toHaveProperty('getAgentBot');
+    expect(inboxesAPI).toHaveProperty('setAgentBot');
   });
   describeWithAPIMock('API calls', context => {
     it('#getCampaigns', () => {