Clarify 'required: false' and 'default: ...' both being present

[blast-hardcheese]

@lolgab correctly pointed out this part of the OpenAPI docs:

Using default with required parameters or properties, for example, with path parameters. This does not make sense – if a value is required, the client must always send it, and the default value is never used.

This PR alters the handling for parameters and properties in the case where getRequired does not return true, and that there is a default present.

Previously, we would liftOptionalTerm and liftOptionalType based purely on getRequired() == true, but now if there is a default value present we leave the values as non-Option-al types and terms.

Practically, that means that if we have a

        - name: p1
          in: query
          required: false
          schema:
            type: integer
            format: int64
            default: 300

we used to get a function like:

def doFoo(p1: Option[Long] = Some(300L)): ...

but now we will get

def doFoo(p1: Long = 300L): ...

This is because the spec mandates that clients always send values in this case, it is invalid to override the default Some(300L) with a None.

[codecov]

Codecov Report

Merging #1534 (83f3602) into master (c107e05) will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master    #1534   +/-   ##
=======================================
  Coverage   84.80%   84.81%           
=======================================
  Files          95       95           
  Lines        5707     5702    -5     
  Branches      141      152   +11     
=======================================
- Hits         4840     4836    -4     
+ Misses        867      866    -1     

Impacted Files	Coverage Δ
...ore/src/main/scala/dev/guardrail/SwaggerUtil.scala	90.43% <100.00%> (ø)
...a/dev/guardrail/generators/LanguageParameter.scala	100.00% <100.00%> (ø)
...ail/generators/java/jackson/JacksonGenerator.scala	95.64% <100.00%> (-0.28%)	⬇️
...enerators/scala/circe/CirceProtocolGenerator.scala	92.70% <100.00%> (ø)
...l/generators/scala/ScalaCollectionsGenerator.scala	65.21% <0.00%> (-4.35%)	⬇️
...yncHttpClient/AsyncHttpClientClientGenerator.scala	94.42% <0.00%> (+0.15%)	⬆️
...la/dev/guardrail/generators/java/syntax/Java.scala	78.62% <0.00%> (+0.68%)	⬆️
...s/scala/dropwizard/DropwizardServerGenerator.scala	84.25% <0.00%> (+0.92%)	⬆️

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