Improve script/category name validation

- Use better error messages with more context.
- Unify their validation logic and share tests.
- Validate also type of the name.
- Refactor node (Script/Category) parser tests for easier future
  changes and cleaner test code (using `TestBuilder` to do dirty work in
  unified way).
- Add more tests. Custom `Error` properties are compared manually due to
  `chai` not supporting deep equality checks (chaijs/chai#1065,
  chaijs/chai#1405).

src/domain/Script.ts

@@ -12,7 +12,7 @@ export class Script extends BaseEntity<string> implements IScript {
   ) {
     super(name);
     if (!code) {
-      throw new Error(`missing code (script: ${name})`);
+      throw new Error('missing code');
     }
     validateLevel(level);
   }