'create( self, trans, page_id, payload **kwd )
* POST /api/pages/{page_id}/revisions
Create a new revision for a page
:param page_id: Add revision to Page with ID=page_id
:param payload: A dictionary containing::
\'title\'     = New title of the page
\'content\'   = New content of the page
:rtype:     dictionary
:returns:   Dictionary with \'success\' or \'error\' element to indicate the result of the request'

@expose_api
def create(self, trans, page_id, payload, **kwd):

    content = payload.get('content', None)
    if (not content):
        raise exceptions.ObjectAttributeMissingException('content    undefined    or    empty')
    page = self._get_page(trans, page_id)
    self._verify_page_ownership(trans, page)
    if ('title' in payload):
        title = payload['title']
    else:
        title = page.title
    content = sanitize_html(content, 'utf-8', 'text/html')
    page_revision = trans.app.model.PageRevision()
    page_revision.title = title
    page_revision.page = page
    page.latest_revision = page_revision
    page_revision.content = content
    session = trans.sa_session
    session.flush()
    return page_revision.to_dict(view='element')
