Improvements, bug fixes and support markdown in activity comments

[djaiss]

This closes #1133 and #1109

Also addresses several bugs.

[codecov]

Codecov Report

Merging #1145 into master will decrease coverage by 0.1%.
The diff coverage is 71.5%.

@@            Coverage Diff             @@
##             master   #1145     +/-   ##
==========================================
- Coverage      38.9%   38.9%   -<.1%     
  Complexity       11      11             
==========================================
  Files           200     200             
  Lines          5256    5260      +4     
==========================================
  Hits           2041    2041             
- Misses         3215    3219      +4

Impacted Files	Coverage Δ	Complexity Δ
app/Http/Controllers/DashboardController.php	11.8% <66.7%> (-4.4%)	0 <0> (ø)
app/Activity.php	83.4% <75%> (-0.8%)	0 <0> (ø)

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[github-actions]

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