Fix race condition when connecting to Fishjam (#214)

## Description

## Motivation and Context

Why is this change required? What problem does it solve? If it fixes an
open
issue, please link to the issue here.

## Documentation impact

- [ ] Documentation update required
- [ ] Documentation updated [in another PR](_)
- [ ] No documentation update required

## Types of changes

- [ ] Bug fix (non-breaking change which fixes an issue)
- [ ] New feature (non-breaking change which adds functionality)
- [ ] Breaking change (fix or feature that would cause existing
functionality to
      not work as expected)

Author: roznawsk

packages/fishjam-proto/protos

@@ -42,6 +42,9 @@ export type AgentEvents = { [K in ExpectedAgentEvents]: (message: NonNullable<Re
 export class FishjamAgent extends (EventEmitter as new () => TypedEmitter<AgentEvents>) {
   private readonly client: WebSocket;
 
+  private resolveConnectionPromise: ((value: void | PromiseLike<void>) => void) | null = null;
+  private readonly connectionPromise: Promise<void>;
+
   constructor(config: FishjamConfig, agentToken: string, callbacks?: AgentCallbacks) {
     super();
 
@@ -57,6 +60,17 @@ export class FishjamAgent extends (EventEmitter as new () => TypedEmitter<AgentE
 
     this.client.onmessage = (message) => this.dispatchNotification(message);
     this.client.onopen = () => this.setupConnection(agentToken);
+
+    this.connectionPromise = new Promise<void>((resolve) => {
+      this.resolveConnectionPromise = resolve;
+    });
+  }
+
+  /**
+   * Await Agent connection to Fishjam.
+   */
+  public async awaitConnected(): Promise<void> {
+    return this.connectionPromise;
   }
 
   /**
@@ -132,6 +146,11 @@ export class FishjamAgent extends (EventEmitter as new () => TypedEmitter<AgentE
     const auth = AgentRequest.encode({ authRequest: { token: agentToken } }).finish();
 
     this.client.send(auth);
+
+    if (this.resolveConnectionPromise) {
+      this.resolveConnectionPromise();
+      this.resolveConnectionPromise = null;
+    }
   }
 
   private isExpectedEvent(notification: string): notification is ExpectedAgentEvents {

packages/js-server-sdk/src/agent.ts

@@ -129,6 +129,7 @@ export class FishjamClient {
         data: { data },
       } = response;
       const agent = new FishjamAgent(this.fishjamConfig, data.token, callbacks);
+      await agent.awaitConnected();
 
       return { agent: agent, peer: data.peer as Peer };
     } catch (error) {