dlang: support `saladVersion`

[tom-tan]

This request makes the saladVersion field supported by the dlang code-generated parser. This change is already tested with schema-salad-d commit: 1170e1b1.

It improves the error and warning messages when users use version-specific or platform-specific features such as supporting nested typeDSL. This request does not include such changes but they will be done in the schema-salad-d rather than the code-generated parser.

TODO:

• [x] Replace Either with SumType Union. It is not related with saladVersion but it is necessary to minimize breaking changes

[codecov[bot]]

Codecov Report

Merging #715 (32edb67) into main (ff30991) will increase coverage by 0.00%. The diff coverage is 100.00%.

@@           Coverage Diff           @@
##             main     #715   +/-   ##
=======================================
  Coverage   83.71%   83.72%           
=======================================
  Files          22       22           
  Lines        4507     4509    +2     
  Branches     1244     1244           
=======================================
+ Hits         3773     3775    +2     
  Misses        469      469           
  Partials      265      265           

Files Changed	Coverage Δ
schema_salad/codegen.py	94.64% <ø> (ø)
schema_salad/dlang_codegen.py	84.37% <100.00%> (+0.19%)	:arrow_up:

[tom-tan]

Thanks!