DPMMA-2222 Email click heatmap

[patrykgruszka]

Q	A
Bug fix? (use the a.b branch)	[ N ]
New feature/enhancement? (use the a.x branch)	[ Y ]
Deprecations?	[ N ]
BC breaks? (use the c.x branch)	[ N ]
Automated tests included?	[ Y ]
Related user documentation PR URL	mautic/mautic-documentation#...
Related developer documentation PR URL	mautic/developer-documentation#...
Issue(s) addressed	Fixes #...

Description:

This PR adds click heatmap visualization to emails in Mautic admin panel.

Preview:

Steps to test this PR:

1. Open this PR on Gitpod or pull down for testing locally (see docs on testing PRs here)
2. Create a new email with some links
3. Send the email to contacts and generate some clicks
4. Open the email view and select the Click heatmap from the dropdown next to the email controls:
   
5. Test that everything is displayed correctly

[codecov]

Codecov Report

Merging #12696 (86f022b) into 5.x (c86f0ee) will increase coverage by 0.10%.
Report is 222 commits behind head on 5.x.
The diff coverage is 85.00%.

@@             Coverage Diff              @@
##                5.x   #12696      +/-   ##
============================================
+ Coverage     58.45%   58.56%   +0.10%     
- Complexity    33597    33607      +10     
============================================
  Files          2183     2180       -3     
  Lines        101716   101698      -18     
============================================
+ Hits          59454    59555     +101     
+ Misses        42262    42143     -119     

Files Changed	Coverage Δ
.../bundles/EmailBundle/Controller/AjaxController.php	62.75% <85.00%> (+3.55%)	⬆️

... and 59 files with indirect coverage changes

[PatrickJenkner]

Just tested it and everything works as described (and looks great)!
Only one small thing: If there are multiple links linking to the same URL, both of them get the same statistics.

I never actually clicked on the left one. This is probably intentional, just wanted to mention it.

[patrykgruszka]

@PatrickJenkner thanks for your review! Yes, at the moment Mautic doesn't track the same links in emails individually and this PR doesn't change this behaviour. I've come across this problem during my analysis and there is an option to track the same link by adding some parameters to the link.

[escopecz]

Please check if my comments make sense.

[patrykgruszka]

@escopecz makes sense. I have made the changes.

[escopecz]

Seems to be working fine and the code looks neat too.

[RCheesley]

@patrykgruszka or @PatrickJenkner would you be up for making a PR to https://github.com/mautic/user-documentation on the 5.x branch to add the detail about this feature?

[mautibot]

This pull request has been mentioned on Mautic Forums. There might be relevant details there:

https://forum.mautic.org/t/announcing-the-mautic-5-release-candidate/29967/1

[mautibot]

This pull request has been mentioned on Mautic Forums. There might be relevant details there:

https://forum.mautic.org/t/mautic-5-beyond-expectations-beyond-limits/30459/1