Add support for projects_v2 and projects_v2_item webhook events

[nikpivkin]

Closes#2867

Added support for projects_v2 and projects_v2_item webhook events.

[codecov]

Codecov Report

Merging #2868 (1ecdb37) into master (899235e) will increase coverage by 0.00%.
Report is 1 commits behind head on master.
The diff coverage is 100.00%.

@@ Coverage Diff @@## master #2868 +/- ##
=======================================
Coverage 98.06% 98.07% =======================================
Files 138 139 +1 Lines 12327 12346 +19 =======================================
+ Hits 12089 12108 +19 
Misses 162 162 Partials 76 76 

Files Changed	Coverage Δ
github/event_types.go	100.00% <ø> (ø)
github/messages.go	100.00% <ø> (ø)
github/event.go	100.00% <100.00%> (ø)

... and 2 files with indirect coverage changes

[gmlewis]

This PR has significant conflicts with #2865 due to said PR dramatically changing the internals for webhook events (which will hopefully also reduce the maintenance burden and increase the simplicity of future PRs like this one).

So I apologize for the timing.

We can either move forward with this PR and have more work required in #2865 or we can move forward with #2865 then require changes here.

I'm honestly fine either way.

Do you have a preference @nikpivkin ?
Or do you have a preference, @evankanderson?

[evankanderson]

I'm happy either way; I'll be updating my PR tomorrow probably

[gmlewis]

Thank you, @nikpivkin !
Just a few minor tweaks, please before proceeding.

[gmlewis]

Thank you, @nikpivkin !
LGTM.

Awaiting second LGTM+Approval from any other contributor to this repo before merging.
(Maybe @evankanderson has time so that this can be merged before work is continued on #2865 ?)

[evankanderson]

Not sure if my review/approval helps, but LGTM. Double checked that the types seem to match the documentation.

[gmlewis]

Not sure if my review/approval helps, but LGTM. Double checked that the types seem to match the documentation.

Yes it does, as you are a valued contributor to this repo. Thank you, @evankanderson !
Merging.