Breaking: Convert Object.assign to spread operator

This ends support for Node 6

Author: kadamwhite

lib/constructors/wp-request.js

@@ -683,7 +683,10 @@ WPRequest.prototype.setHeaders = function( headers, value ) {
 		headers = keyValToObj( headers, value );
 	}
 
-	this._options.headers = Object.assign( {}, this._options.headers || {}, headers );
+	this._options.headers = {
+		...( this._options.headers || {} ),
+		...headers,
+	};
 
 	return this;
 };

tests/unit/wpapi.js

@@ -588,12 +588,16 @@ describe( 'WPAPI', () => {
 			} );
 
 			it( 'does not impact or overwrite unspecified transport methods', () => {
-				const originalMethods = Object.assign( {}, site._options.transport );
+				const originalMethods = {
+					...site._options.transport,
+				};
 				site.transport( {
 					get() {},
 					put() {},
 				} );
-				const newMethods = Object.assign( {}, site._options.transport );
+				const newMethods = {
+					...site._options.transport,
+				};
 				expect( newMethods.delete ).toBe( originalMethods.delete );
 				expect( newMethods.post ).toBe( originalMethods.post );