fix(types): Make name required on transaction class (#2949)

This allows the class to implement the interface, where `name` has always been required.

packages/tracing/src/transaction.ts

@@ -1,12 +1,12 @@
 import { getCurrentHub, Hub } from '@sentry/hub';
-import { TransactionContext } from '@sentry/types';
+import { Transaction as TransactionInterface, TransactionContext } from '@sentry/types';
 import { isInstanceOf, logger } from '@sentry/utils';
 
 import { Span as SpanClass, SpanRecorder } from './span';
 
 /** JSDoc */
-export class Transaction extends SpanClass {
-  public name?: string;
+export class Transaction extends SpanClass implements TransactionInterface {
+  public name: string;
 
   /**
    * The reference to the current hub.
@@ -29,9 +29,7 @@ export class Transaction extends SpanClass {
       this._hub = hub as Hub;
     }
 
-    if (transactionContext.name) {
-      this.name = transactionContext.name;
-    }
+    this.name = transactionContext.name ? transactionContext.name : '';
 
     this._trimEnd = transactionContext.trimEnd;
   }