[Polymorphism Prep] Expose private KotlinGenerator methods in SharedCodegen

[macisamuele]

This PR does some preparatory work for #103 .
In order to achieve polymorphism support we need to extract few functionalities from KotlinGenerator to SharedCodegen.

I totally understand that this PR seems disconnected and doesn't really explain why certain features are moved back to SharedCodegen or why we do even need to iterate over all CodegenModel.*vars.
In order to provide a better visibility I would suggest to check the potential draft of polymorphism on macisamuele/swagger-gradle-codegen@maci-polymmorphism

[macisamuele]

I've rebased this branch on top of the laster master to remove the merge conflicts.

@cortinico could you please have a look to this CR?

This provides a starting point for for #103 and by itself does not provide any change that deserve a major release, so it could be merged even if we're not yet planning on having the 2.0.0 release

[cortinico]

Left several comments.
Maybe having also the second part will help understand some of the changes?
Generally looks good, but having some tests will be beneficial 👍

[cortinico]

Seems like the CodegenModelVar here is unused. Can you please remove it?

[macisamuele]

I'd rather prefer having it as it will be used in the subsequent branch :)

[cortinico]

This class is probably not needed at all and the same behavior can be achieved with an extension function:

fun CodegenModel.forEachVarAttribute(
        action: (MutableList<CodegenProperty>) -> Unit
) {
    listOf<MutableList<CodegenProperty>>(
            this.allVars,
            this.optionalVars,
            this.parentVars,
            this.readOnlyVars,
            this.readWriteVars,
            this.requiredVars,
            this.vars).forEach { action(it) }
}

[macisamuele]

The enums and stuff are mostly needed to ensure that we can have information on which list of variables we're working on.
This is something needed in the usages that will be proposed on the subsequent PR

[cortinico]

I'm having a hard time understanding the use case of this.

[macisamuele]

@cortinico it will take me some time (maybe a few weeks) to provide changes on this PR.
Currently my laptop is not powerful enough to run all the tasks ;)

Maybe having also the second part will help understand some of the changes

The current branch that fully targets #103 is avaiblable on https://github.com/macisamuele/swagger-gradle-codegen/tree/maci-polymorphism .

[cortinico]

@cortinico it will take me some time (maybe a few weeks) to provide changes on this PR.
Currently my laptop is not powerful enough to run all the tasks ;)

No problem, let's keep this opened for now.

[codecov]

Codecov Report

Merging #104 (249f4d2) into master (5318347) will increase coverage by 1.81%.
The diff coverage is 82.92%.

❗ Current head 249f4d2 differs from pull request most recent head cdd09a3. Consider uploading reports for the commit cdd09a3 to get more accurate results

@@             Coverage Diff              @@
##             master     #104      +/-   ##
============================================
+ Coverage     70.83%   72.65%   +1.81%     
- Complexity      138      147       +9     
============================================
  Files            11       12       +1     
  Lines           576      607      +31     
  Branches         87       80       -7     
============================================
+ Hits            408      441      +33     
- Misses          118      122       +4     
+ Partials         50       44       -6     

Impacted Files	Coverage Δ
.../src/main/java/com/yelp/codegen/KotlinGenerator.kt	83.62% <ø> (+0.83%)	⬆️
...in/src/main/java/com/yelp/codegen/SharedCodegen.kt	63.93% <77.41%> (+6.14%)	⬆️
...ain/java/com/yelp/codegen/utils/CodegenModelVar.kt	100.00% <100.00%> (ø)
...ugin/plugin/src/main/java/com/yelp/codegen/Main.kt	98.33% <0.00%> (-0.06%)	⬇️
...rc/main/java/com/yelp/codegen/utils/StringUtils.kt	100.00% <0.00%> (+11.11%)	⬆️

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