WEB-112: Sanitize GSIM fields before calculateLoanSchedule to avoid NPE

- Add sanitizeLoanPayload method to LoansService to remove unsafe GSIM linkage fields (linkAccountId, linkAccountOwnerId, linkAccountOwnerName, linkedSavingsAccount) before posting to backend
- Apply sanitization in calculateLoanSchedule endpoint to prevent payload from triggering NullPointerException in Fineract LoanScheduleCalculationPlatformServiceImpl
- Add unit tests for payload sanitization to verify forbidden fields are removed and allowed fields are preserved
- Fixes 500 Internal Server Error when generating repayment schedule for GLIM loans linked to GSIM accounts

Author: deepaksoni47

src/app/loans/loans.service.spec.ts

@@ -0,0 +1,94 @@
+import { TestBed } from '@angular/core/testing';
+import { HttpTestingController, provideHttpClientTesting } from '@angular/common/http/testing';
+import { provideHttpClient } from '@angular/common/http';
+import { LoansService } from './loans.service';
+import { SettingsService } from 'app/settings/settings.service';
+import { Dates } from 'app/core/utils/dates';
+
+describe('LoansService', () => {
+  let service: LoansService;
+  let httpMock: HttpTestingController;
+
+  beforeEach(() => {
+    const mockSettings: Partial<SettingsService> = {
+      language: { name: 'English', code: 'en' },
+      dateFormat: 'yyyy-MM-dd',
+      businessDate: new Date(),
+      maxFutureDate: new Date()
+    };
+    const mockDates: Partial<Dates> = {
+      formatDate: (d: any) => d,
+      formatDateAsString: (d: any) => String(d)
+    } as any;
+
+    TestBed.configureTestingModule({
+      providers: [
+        LoansService,
+        provideHttpClient(),
+        provideHttpClientTesting(),
+        { provide: SettingsService, useValue: mockSettings },
+        { provide: Dates, useValue: mockDates }]
+    });
+    service = TestBed.inject(LoansService);
+    httpMock = TestBed.inject(HttpTestingController);
+  });
+
+  afterEach(() => {
+    httpMock.verify();
+  });
+
+  it('should sanitize all GSIM fields before posting calculateLoanSchedule', () => {
+    const payload = {
+      principal: 1000,
+      linkAccountId: 42,
+      linkAccountOwnerName: 'Alice',
+      linkedSavingsAccount: { id: 5 },
+      nested: {
+        linkAccountOwnerId: 7,
+        linkAccountOwnerName: 'Bob',
+        ok: 'keep'
+      },
+      members: [
+        { id: 1, linkAccountId: 99 },
+        { id: 2, name: 'foo', linkedSavingsAccount: { id: 9 } }
+      ]
+    } as any;
+
+    const original = JSON.parse(JSON.stringify(payload));
+
+    service.calculateLoanSchedule(payload).subscribe(() => {});
+
+    const req = httpMock.expectOne('/loans?command=calculateLoanSchedule');
+    expect(req.request.method).toBe('POST');
+
+    const body = req.request.body;
+
+    // All forbidden keys should be removed at every depth
+    expect(body.linkAccountId).toBeUndefined();
+    expect(body.linkAccountOwnerName).toBeUndefined();
+    expect(body.linkedSavingsAccount).toBeUndefined();
+    expect(body.nested.linkAccountOwnerId).toBeUndefined();
+    expect(body.nested.linkAccountOwnerName).toBeUndefined();
+    expect(body.members[0].linkAccountId).toBeUndefined();
+    expect(body.members[1].linkedSavingsAccount).toBeUndefined();
+
+    // Allowed keys should be preserved
+    expect(body.principal).toBe(1000);
+    expect(body.nested.ok).toBe('keep');
+    expect(body.members[1].name).toBe('foo');
+
+    // Original caller payload must remain unmutated
+    expect(payload).toEqual(original);
+
+    req.flush({});
+  });
+
+  it('should keep non-object primitives intact', () => {
+    const payload = { value: 1, text: 'abc' };
+    service.calculateLoanSchedule(payload).subscribe(() => {});
+    const req = httpMock.expectOne('/loans?command=calculateLoanSchedule');
+    expect(req.request.body.value).toBe(1);
+    expect(req.request.body.text).toBe('abc');
+    req.flush({});
+  });
+});

src/app/loans/loans.service.ts

@@ -30,6 +30,13 @@ export interface WorkingCapitalLoanDiscountUpdateRequest {
   providedIn: 'root'
 })
 export class LoansService {
+  private static readonly FORBIDDEN_LOAN_PAYLOAD_KEYS: ReadonlySet<string> = new Set([
+    'linkAccountId',
+    'linkAccountOwnerId',
+    'linkAccountOwnerName',
+    'linkedSavingsAccount'
+  ]);
+
   private http = inject(HttpClient);
   private settingsService = inject(SettingsService);
   private dateUtils = inject(Dates);
@@ -701,8 +708,29 @@ export class LoansService {
     return this.http.post('/batches?enclosingTransaction=true', payload);
   }
 
+  /**
+   * Calculate repayment schedule preview.
+   * Sanitize payload to avoid sending GSIM-linked fields that may crash backend.
+   */
   calculateLoanSchedule(payload: any): Observable<any> {
-    return this.http.post('/loans?command=calculateLoanSchedule', payload);
+    const sanitized = this.sanitizeLoanPayload(payload);
+    return this.http.post('/loans?command=calculateLoanSchedule', sanitized);
+  }
+
+  /**
+   * Remove potentially unsafe GSIM linkage fields from payload recursively.
+   * This is a defensive workaround until backend validation is fixed in Fineract.
+   * Does not mutate the caller's payload; returns a new sanitized copy.
+   */
+  private sanitizeLoanPayload(obj: any): any {
+    if (obj === null || typeof obj !== 'object') return obj;
+    if (Array.isArray(obj)) return obj.map((item) => this.sanitizeLoanPayload(item));
+    const out: Record<string, any> = {};
+    for (const key of Object.keys(obj)) {
+      if (LoansService.FORBIDDEN_LOAN_PAYLOAD_KEYS.has(key)) continue;
+      out[key] = this.sanitizeLoanPayload(obj[key]);
+    }
+    return out;
   }
 
   attachLoanOriginator(loanId: string, originatorId: string): Observable<any> {