Fix: Omit Nullable in JSON when undefined; preserve undefined in propertyValueToBoolean

Author: diegomvh

projects/angular-odata/schematics/apigen/metadata/csdl/csdl-structural-property.ts

@@ -29,12 +29,16 @@ export abstract class CsdlStructuralProperty extends CsdlAnnotable {
   }
 
   override toJson() {
-    return {
+    const json: { [key: string]: any } = {
       ...super.toJson(),
       Name: this.Name,
       Type: this.Collection ? `Collection(${this.Type})` : this.Type,
       Nullable: this.Nullable,
-    } as { [key: string]: any };
+    };
+    if (this.Nullable !== undefined) {
+      json['Nullable'] = this.Nullable;
+    }
+    return json;
   }
 
   isEdmType(): boolean {

projects/angular-odata/schematics/apigen/metadata/parser.ts

@@ -592,7 +592,9 @@ export class ODataMetadataParser {
   }
 
   protected propertyValueToBoolean(attributeValue?: string) {
-    return attributeValue !== undefined ? attributeValue === 'true' : false;
+    return attributeValue !== undefined && attributeValue === 'true' ?  true : 
+      attributeValue !== undefined && attributeValue === 'false' ? false :
+      undefined;
   }
 
   protected propertyValueToDate(attributeValue?: string) {