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).

tests/unit/domain/Script.spec.ts

@@ -24,12 +24,10 @@ describe('Script', () => {
       describe('throws when missing', () => {
         itEachAbsentObjectValue((absentValue) => {
           // arrange
-          const name = 'script-name';
-          const expectedError = `missing code (script: ${name})`;
+          const expectedError = 'missing code';
           const code: IScriptCode = absentValue;
           // act
           const construct = () => new ScriptBuilder()
-            .withName(name)
             .withCode(code)
             .build();
           // assert