Provide support for changelogs

Hi,

Recently I was playing with data and the provider uploaded a new version. I realised they didn't describe their changes. I thought this would be handy if CKAN could provide support for some sort of changelog facility (even a simple text area with the date of the upload).

This would be quite useful.

(ref: https://github.com/ckan/ckan/issues/1988)

Start by reviewing the linked CKAN issue 1988 and clarifying what a changelog should contain and where it should appear. The proposal mentions a simple text area with an upload date, but no files, tests, or concrete acceptance criteria are identified; completion would require an agreed scope and corresponding implementation and tests.

Written by the indexing model from the issue text.