id attribute of <g:form> is ignored

[donalmurtagh]

Steps to Reproduce

1. Create a new Grails 3.3.2 app with the web profile
2. Add a User domain class with a name property
3. Run grails generate-all user
4. Add an id property to the form for creating a new user

<g:form resource="${this.user}" method="POST" id="create-user-form">
...
</g:form>

Expected Behaviour

The HTML for this form should have an id="create-user-form" attribute

Actual Behaviour

The HTML for this form does not have an id="create-user-form" attribute.
Incidentally, the resource attribute of the g:form tag is not documented

Environment Information

• Operating System: Mac OS X
• Grails Version: 3.3.2
• JDK Version: 1.8.0_66
• Container Version (If Applicable): Tomcat