WIP: Start version 2 with some cleanups

[dbu]

Q	A
Bug fix?	no
New feature?	no
BC breaks?	yes
Deprecations?	no
Related tickets	BC breaking changes from #29
Documentation	-
License	MIT

What's in this PR?

Some BC breaking changes that clean up the mock client. To be merged when we want to start with version 2.

Checklist

• [x] Updated CHANGELOG.md to describe BC breaks / deprecations | new feature | bugfix
• no documentation changes needed

TODO

• [ ] Use PSR response factory instead of httplug factory
• [ ] Only allow PSR-18 and httplug exceptions to be configured on the mock client
• [ ] Bump to version 2 of httplug and provide psr/http-client-implementation to fix #38

[Nyholm]

Why do you want to release a new major version of this client?

[dbu]

i don't want to do that now, just wanted to keep the cleanups that we agreed are useful but are BC break. i don't intend to merge this anytime soon.

[dbu]

as per discussion in #36 i want to merge this soonish. does that change if we want to drop httplug 1 support? the cost of supporting both is low and i think there would be value in keeping that so that libraries can test with both httplug 1 and 2 for a while.

[Taluu]

Any update on this PR ? :}

[dbu]

i did not find the time to continue on this. if you want to wrap things up, more than happy to review things ;-)

[Taluu]

I'll give it a try whenever I get some time (not right now...). Do not wait on me though :laughing: