Updates to testing suite.

Merge pull request #36 from Tailchakra/main

Fixing history according to issue #35

Merge pull request #33 from danielpilot/allow-null-listen-url

Allow null listen URL

#29 -- Fix JSON serialization.

Fixes #30 -- Update type hinting on Permissions endpoint.

Fixes #29 -- Update name for "new password" on user API.

Merge pull request #28 from kmaid/patch-1

API Client doesn't set accept content type

Make Guzzle config options-based to prepare for Guzzle retiring getConfig().

Allow null formats on RemoteDtos too.

Package upgrades and PhpStan fixes.

One more test fix.

Test suite fixes.