Fix callbacks

[andrykonchin]

Reviewed callbacks and fixed Rails compatibility issues:

• fixed order of save and create/update callbacks
• removed before_/around_ initialize callback
• run after_touch callback in #touch, #increment! and #decrement! methods

Also there are the following fixes of the #touch method:

• it doesn't save other modified attributes - only timestamps
• it doesn't perform validation and doesn't execute save/create/update callbacks
• it accepts not one attribute name but a list of names
• it accepts a :time option with timestamp value

[codecov]

Codecov Report

Merging #634 (dc0e88a) into master (1f09be1) will increase coverage by 0.02%.
The diff coverage is 100.00%.

❗ Current head dc0e88a differs from pull request most recent head fbb690e. Consider uploading reports for the commit fbb690e to get more accurate results

@@            Coverage Diff             @@
##           master     #634      +/-   ##
==========================================
+ Coverage   90.24%   90.27%   +0.02%     
==========================================
  Files          61       61              
  Lines        3127     3136       +9     
==========================================
+ Hits         2822     2831       +9     
  Misses        305      305              

Impacted Files	Coverage Δ
lib/dynamoid/components.rb	100.00% <100.00%> (ø)
lib/dynamoid/persistence.rb	98.15% <100.00%> (+0.09%)	⬆️

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[github-actions]

Package	Line Rate	Health
dynamoid	90%	➖
Summary	90% (2831 / 3136)	➖

Minimum allowed line rate is 90%