[LuisFigueroaG]

docs/confluence.rst documents confluence.get_page_id(space, title, type="page"), and both the Server client and ConfluenceV2 have it. The Cloud client (Confluence(url="https://<site>.atlassian.net") / ConfluenceCloud) doesn't, so code that worked on 4.x fails with:

AttributeError: 'Cloud' object has no attribute 'get_page_id'

This came up in #1658, where adding it to Cloud was mentioned but it hasn't landed yet.

This adds get_page_id(space, title, type="page") to Cloud, with the same arguments as the Server client. It uses the same V2 lookup as page_exists(): resolve the space key with GET /wiki/api/v2/spaces?keys=..., then query api/v2/pages (or api/v2/blogposts for type="blogpost", as in #1703) by space-id and title. It returns the first ID as a string, or None when the space or the page isn't found, like ConfluenceV2.get_page_id().

To avoid copying that lookup, it moves into a small private helper that both page_exists() and get_page_id() call. page_exists() sends the same requests and returns the same results as before.

Tests: added five test_get_page_id_* tests to tests/confluence/test_confluence_cloud.py (pages, blog posts, not found, unknown space, and a call through Confluence(url="https://test.atlassian.net")); they fail on master with the error above. The existing page_exists tests pass unchanged. The full pytest suite and tox -e mypy pass, and black and flake8 are clean on the changed files. I haven't run it against a real Confluence Cloud site.