[book] remove dbapi documentation Move some still-relevant doc related to the RQL connection API to the 'sessions' section. It might make sense to move this back outside of the "Repository development" chapter at some point since this is relevant in other contexts.

[uilib] `uilib.js` helper now honors explicit JSString (closes #4959538) Previously, if a JSString was inside a nested container (i.e. list or dict), it was handled as a string, not a verbatim js chunk (see docstring and test). So the following code:: >>> str(js.cw.pouet(1, {'callback': JSString('cw.mycallback')}) resulted in:: "cw.pouet(1, {'callback': 'cw.mycallback')})" while we expect (note the removed quotes):: "cw.pouet(1, {'callback': cw.mycallback)})" We use ``cubiweb.utils.js_dumps`` instead of ``cubicweb.utils.json_dumps`` which is aware of JSString.

[dbapi] remove the dbapi module and its immediate remaining users We suppress toolsutils.config_connect, which has currently only one known user (the email cube), which is being patched. It can be replaced with utils.admincnx function for a local access. Next will come a series to: * remove the session backward compatibility * fold ClientConnection into Connection Closes #3933480.

[web/views] remove dbapi usage from 'gc' view

[sqlite] Fix integrity error parsing Up to sqlite 3.7, integrity error message may be in the singular form if only one column is in the unique index. Closes #5224632

[postgres] fix limit_size regexp to properly remove one char tags like <p>. Closes #5221847

[postgres] _regproc.postgres.sql should be reloadable

[mail] include Date header in generated mails (closes #5271058) Mails without Date gets flagged as spam. Plus it's wrong anyway.

[doc] mention datadir-url configuration option in release notes Related to #5204550

[web] add test for datadir-url option (related to #5204550)