refactor: Restructure source code folder

This way the location of certain classes should make more sense

test/unit/http/input/metadata/SlugParser.test.ts

@@ -0,0 +1,35 @@
+import { SlugParser } from '../../../../../src/http/input/metadata/SlugParser';
+import { RepresentationMetadata } from '../../../../../src/http/representation/RepresentationMetadata';
+import type { HttpRequest } from '../../../../../src/server/HttpRequest';
+import { BadRequestHttpError } from '../../../../../src/util/errors/BadRequestHttpError';
+import { SOLID_HTTP } from '../../../../../src/util/Vocabularies';
+
+describe('A SlugParser', (): void => {
+  const parser = new SlugParser();
+  let request: HttpRequest;
+  let metadata: RepresentationMetadata;
+
+  beforeEach(async(): Promise<void> => {
+    request = { headers: {}} as HttpRequest;
+    metadata = new RepresentationMetadata();
+  });
+
+  it('does nothing if there is no slug header.', async(): Promise<void> => {
+    await expect(parser.handle({ request, metadata })).resolves.toBeUndefined();
+    expect(metadata.quads()).toHaveLength(0);
+  });
+
+  it('errors if there are multiple slug headers.', async(): Promise<void> => {
+    request.headers.slug = [ 'slugA', 'slugB' ];
+    const result = parser.handle({ request, metadata });
+    await expect(result).rejects.toThrow(BadRequestHttpError);
+    await expect(result).rejects.toThrow('Request has multiple Slug headers');
+  });
+
+  it('stores the slug metadata.', async(): Promise<void> => {
+    request.headers.slug = 'slugA';
+    await expect(parser.handle({ request, metadata })).resolves.toBeUndefined();
+    expect(metadata.quads()).toHaveLength(1);
+    expect(metadata.get(SOLID_HTTP.slug)?.value).toBe('slugA');
+  });
+});