made MongoServerError.errorResponse required + casted resulting type errors

Author: aditi-khare-mongoDB

src/error.ts

@@ -201,7 +201,7 @@ export class MongoError extends Error {
  */
 export class MongoServerError extends MongoError {
   /** Raw error result document returned by server. */
-  errorResponse?: ErrorDescription;
+  errorResponse: ErrorDescription;
   codeName?: string;
   writeConcernError?: Document;
   errInfo?: Document;

src/sdam/server.ts

@@ -171,7 +171,7 @@ export class Server extends TypedEventEmitter<ServerEvents> {
       this.monitor.on(event, (e: any) => this.emit(event, e));
     }
 
-    this.monitor.on('resetServer', (error: MongoError) => markServerUnknown(this, error));
+    this.monitor.on('resetServer', (error: MongoServerError) => markServerUnknown(this, error));
     this.monitor.on(Server.SERVER_HEARTBEAT_SUCCEEDED, (event: ServerHeartbeatSucceededEvent) => {
       this.emit(
         Server.DESCRIPTION_RECEIVED,
@@ -369,7 +369,7 @@ export class Server extends TypedEventEmitter<ServerEvents> {
       // clear for the specific service id.
       if (!this.loadBalanced) {
         error.addErrorLabel(MongoErrorLabel.ResetPool);
-        markServerUnknown(this, error);
+        markServerUnknown(this, error as MongoServerError);
       } else if (connection) {
         this.pool.clear({ serviceId: connection.serviceId });
       }
@@ -385,7 +385,7 @@ export class Server extends TypedEventEmitter<ServerEvents> {
             if (shouldClearPool) {
               error.addErrorLabel(MongoErrorLabel.ResetPool);
             }
-            markServerUnknown(this, error);
+            markServerUnknown(this, error as MongoServerError);
             process.nextTick(() => this.requestCheck());
           }
         }

src/sdam/topology_description.ts

@@ -313,7 +313,7 @@ export class TopologyDescription {
     );
 
     if (descriptionsWithError.length > 0) {
-      return descriptionsWithError[0].error;
+      return descriptionsWithError[0].error as MongoServerError;
     }
 
     return null;