Fix field name to 'required` of ConfigurationParameterDescriptor

The TSP specifies `required` instead of `isRequired`. This commit aligns
the implementation with the specification.

See also:
eclipse-tracecompass-incubator/org.eclipse.tracecompass.incubator#246

Signed-off-by: Bernd Hufmann <bernd.hufmann@ericsson.com>

Author: bhufmann

tsp-typescript-client/fixtures/tsp-client/fetch-configuration-sources-0.json

@@ -8,7 +8,7 @@
 				"keyName": "path",
 				"description": "path description",
 				"dataType": "STRING",
-				"isRequired": "True"
+				"required": "True"
  			},
 			{
 				"keyName": "test1"

tsp-typescript-client/src/models/configuration-source.ts

@@ -55,5 +55,5 @@ export interface ConfigurationParameterDescriptor {
     /**
      * If parameter needs to in the query parameters or not. Default is false. 
      */
-    isRequired?: boolean;
+    required?: boolean;
 }

tsp-typescript-client/src/protocol/tsp-client.test.ts

@@ -539,12 +539,12 @@ describe('HttpTspClient Deserialization', () => {
     expect(paramDesc[0].keyName).toEqual('path');
     expect(paramDesc[0].description).toEqual('path description');
     expect(paramDesc[0].dataType).toEqual('STRING');
-    expect(paramDesc[0].isRequired).toBeTruthy();
+    expect(paramDesc[0].required).toBeTruthy();
 
     expect(paramDesc[1].keyName).toEqual('test1');
     expect(paramDesc[1].description).toBeUndefined();
     expect(paramDesc[1].dataType).toBeUndefined();
-    expect(paramDesc[1].isRequired).toBeUndefined();
+    expect(paramDesc[1].required).toBeUndefined();
     expect(sourceTypes[0].schema).toBeUndefined();
 
     expect(sourceTypes[1].parameterDescriptors).toBeUndefined();