Drop support for logback 1.2

[philsttr]

Drop support for logback 1.2 in preparation for upcoming support for keyValue pairs in slf4j 2 and logback 1.3 in #954

[codecov]

Codecov Report

Merging #970 (ea18315) into main (639c28f) will increase coverage by 0.13%.
The diff coverage is 88.88%.

@@             Coverage Diff              @@
##               main     #970      +/-   ##
============================================
+ Coverage     71.92%   72.05%   +0.13%     
+ Complexity     1356     1353       -3     
============================================
  Files           173      173              
  Lines          5011     4999      -12     
  Branches        519      517       -2     
============================================
- Hits           3604     3602       -2     
+ Misses         1153     1148       -5     
+ Partials        254      249       -5     

Impacted Files	Coverage Δ
...n/java/net/logstash/logback/util/LogbackUtils.java	75.00% <ø> (+10.29%)	⬆️
...ogback/composite/AbstractSequenceJsonProvider.java	90.90% <83.33%> (+3.95%)	⬆️
...nt/LoggingEventFormattedTimestampJsonProvider.java	100.00% <100.00%> (+50.00%)	⬆️
...site/loggingevent/LogstashMarkersJsonProvider.java	94.44% <100.00%> (+9.44%)	⬆️
...gback/composite/loggingevent/TagsJsonProvider.java	96.29% <100.00%> (+6.64%)	⬆️

[analytically]

This is quite some breaking change.

[carl-parrish]

upgrading from 7.3 to 7.4 just destroyed all my unitTests so far this is the only thing I can think that would have that kind of impact. I didn't write the original code any suggestions on what I should look for to see if I had logbook 1.2 dependencies in my code? Any docs on migration?

[philsttr]

Hi @carl-parrish, Check the logback news for details on changes in logback 1.3.