feat: add wagon usage computation and maintenance logging features

- Implemented  utility to calculate wagon usage metrics for train schedules.
- Created  for sending wagons to maintenance with optional notes.
- Added unit tests for train builder maintenance functionalities, including formatting train run labels and building maintenance notes.
- Developed  component for merging train schedules with detailed previews and reasons for merging.
- Introduced  component for selecting wagons with search functionality and selection limits.
- Created  for displaying and filtering audit logs, including detailed views of individual log entries.
- Added  for handling API interactions related to audit logs, including fetching logs and entity types.

apps/edr-freight-api/src/modules/trains/train-builder.maintenance.spec.ts

@@ -0,0 +1,83 @@
+import { buildMaintenanceNotes, formatTrainRunLabel } from './train-builder.service';
+
+describe('formatTrainRunLabel', () => {
+  it('names the train by its export and import run numbers', () => {
+    // What staff actually recognise — NOT the internal code (TRN-LEDGER-PW2).
+    expect(
+      formatTrainRunLabel({
+        exportTrainNumber: '9201',
+        importTrainNumber: '9202',
+        trainNumber: 'TRN-7',
+        code: 'TRN-LEDGER-PW2',
+      }),
+    ).toBe('export 9201 / import 9202');
+  });
+
+  it('shows only the run number that is set', () => {
+    expect(
+      formatTrainRunLabel({ exportTrainNumber: '9201', code: 'TRN-LEDGER-PW2' }),
+    ).toBe('export 9201');
+    expect(
+      formatTrainRunLabel({ importTrainNumber: '9202', code: 'TRN-LEDGER-PW2' }),
+    ).toBe('import 9202');
+  });
+
+  it('falls back to the train number, then the code, when no run is set', () => {
+    expect(formatTrainRunLabel({ trainNumber: 'TRN-7', code: 'TRN-LEDGER-PW2' })).toBe(
+      'TRN-7',
+    );
+    expect(formatTrainRunLabel({ code: 'TRN-LEDGER-PW2' })).toBe('TRN-LEDGER-PW2');
+  });
+
+  it('ignores blank run numbers rather than printing empty labels', () => {
+    expect(
+      formatTrainRunLabel({ exportTrainNumber: '  ', importTrainNumber: null, code: 'C-1' }),
+    ).toBe('C-1');
+  });
+
+  it('never returns an empty label', () => {
+    expect(formatTrainRunLabel({})).toBe('unknown');
+  });
+});
+
+describe('buildMaintenanceNotes', () => {
+  it('records the operator reason together with the train it came off', () => {
+    const notes = buildMaintenanceNotes('export 9201 / import 9202', 'Brake shoe worn through');
+
+    expect(notes.statusLogNote).toBe(
+      'Brake shoe worn through (detached from train export 9201 / import 9202)',
+    );
+    expect(notes.movementNote).toBe(
+      'Sent to maintenance from train export 9201 / import 9202: Brake shoe worn through',
+    );
+  });
+
+  it('still records the train number when no reason is given', () => {
+    // The reason is optional, but which train a wagon left is never optional —
+    // the history has to answer that on its own.
+    const notes = buildMaintenanceNotes('export 9201 / import 9202');
+
+    expect(notes.statusLogNote).toBe('Detached from train export 9201 / import 9202');
+    expect(notes.movementNote).toBe('Sent to maintenance from train export 9201 / import 9202');
+  });
+
+  it('treats a whitespace-only reason as no reason', () => {
+    const notes = buildMaintenanceNotes('export 9201 / import 9202', '   ');
+
+    expect(notes.statusLogNote).toBe('Detached from train export 9201 / import 9202');
+    expect(notes.movementNote).toBe('Sent to maintenance from train export 9201 / import 9202');
+  });
+
+  it('trims padding around a real reason', () => {
+    const notes = buildMaintenanceNotes('export 9201 / import 9202', '  Coupler damage  ');
+
+    expect(notes.statusLogNote).toBe('Coupler damage (detached from train export 9201 / import 9202)');
+    expect(notes.movementNote).toBe('Sent to maintenance from train export 9201 / import 9202: Coupler damage');
+  });
+
+  it('handles a null reason from an older client', () => {
+    expect(buildMaintenanceNotes('export 9201 / import 9202', null).statusLogNote).toBe(
+      'Detached from train export 9201 / import 9202',
+    );
+  });
+});