fix: Enable strict TypeScript settings

src/authentication/Credentials.ts

@@ -2,5 +2,5 @@
  * Credentials identifying an entity accessing or owning data.
  */
 export interface Credentials {
-  webID: string;
+  webID?: string;
 }

src/authentication/SimpleCredentialsExtractor.ts

@@ -14,5 +14,6 @@ export class SimpleCredentialsExtractor extends CredentialsExtractor {
     if (input.headers.authorization) {
       return { webID: input.headers.authorization };
     }
+    return {};
   }
 }