show chatops proxy error (#4719)

# What this PR does

show chatops proxy error if present in query params

## Which issue(s) this PR closes

Related to https://github.com/grafana/oncall-gateway/issues/255

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## Checklist

- [ ] Unit, integration, and e2e (if applicable) tests updated
- [x] Documentation added (or `pr:no public docs` PR label added if not
required)
- [x] Added the relevant release notes label (see labels prefixed w/
`release:`). These labels dictate how your PR will
    show up in the autogenerated release notes.

grafana-plugin/src/pages/settings/tabs/ChatOps/ChatOps.helpers.ts

@@ -0,0 +1,11 @@
+import { LocationHelper } from 'utils/LocationHelper';
+import { openErrorNotification } from 'utils/utils';
+
+export const handleChatOpsQueryParamError = () => {
+  const error = LocationHelper.getQueryParam('error');
+
+  if (error) {
+    openErrorNotification(error);
+    LocationHelper.update({ error: undefined }, 'partial');
+  }
+};

grafana-plugin/src/pages/settings/tabs/ChatOps/ChatOps.tsx

@@ -15,6 +15,8 @@ import { useStore } from 'state/useStore';
 import { withMobXProviderContext } from 'state/withStore';
 import { LocationHelper } from 'utils/LocationHelper';
 
+import { handleChatOpsQueryParamError } from './ChatOps.helpers';
+
 import styles from './ChatOps.module.css';
 
 const cx = cn.bind(styles);
@@ -38,6 +40,7 @@ export class _ChatOpsPage extends React.Component<ChatOpsProps, ChatOpsState> {
   componentDidMount() {
     const tab = LocationHelper.getQueryParam('chatOpsTab');
 
+    handleChatOpsQueryParamError();
     this.handleChatopsTabChange(tab || ChatOpsTab.Slack);
   }