fix: add CI trigger path for new sample and align nullableReturnType in api_doc template

- Add workflow trigger path for kotlin-jvm-spring-3-restclient-nullable-return
  sample so changes in that directory actually run CI.
- Propagate nullableReturnType into the signature and return-type sections
  of api_doc.mustache (previously only the example code showed the '?').
- Regenerate DefaultApi.md for the new sample to reflect the fix.

Author: takkiraz

.github/workflows/samples-kotlin-client.yaml

@@ -6,12 +6,14 @@ on:
       - 'samples/client/petstore/kotlin*/**'
       - 'samples/client/others/kotlin-jvm-okhttp-parameter-tests/**'
       - samples/client/others/kotlin-integer-enum/**
+      - samples/client/others/kotlin-jvm-spring-3-restclient-nullable-return/**
   pull_request:
     paths:
       - 'samples/client/petstore/kotlin*/**'
       - 'samples/client/others/kotlin-jvm-okhttp-parameter-tests/**'
       - samples/client/others/kotlin-integer-enum/**
       - samples/client/others/kotlin-oneOf-anyOf-kotlinx-serialization/**
+      - samples/client/others/kotlin-jvm-spring-3-restclient-nullable-return/**
 
 jobs:
   build:

modules/openapi-generator/src/main/resources/kotlin-client/api_doc.mustache

@@ -12,7 +12,7 @@ All URIs are relative to *{{basePath}}*
 {{#operation}}
 <a id="{{operationId}}"></a>
 # **{{operationId}}**
-> {{#returnType}}{{.}} {{/returnType}}{{operationId}}({{#allParams}}{{{paramName}}}{{^-last}}, {{/-last}}{{/allParams}})
+> {{#returnType}}{{.}}{{#nullableReturnType}}?{{/nullableReturnType}} {{/returnType}}{{operationId}}({{#allParams}}{{{paramName}}}{{^-last}}, {{/-last}}{{/allParams}})
 
 {{summary}}{{#notes}}
 
@@ -55,7 +55,7 @@ This endpoint does not need any parameter.
 
 ### Return type
 
-{{#returnType}}{{#returnTypeIsPrimitive}}**{{returnType}}**{{/returnTypeIsPrimitive}}{{^returnTypeIsPrimitive}}{{#generateModelDocs}}[**{{returnType}}**]({{returnBaseType}}.md){{/generateModelDocs}}{{^generateModelDocs}}**{{returnType}}**{{/generateModelDocs}}{{/returnTypeIsPrimitive}}{{/returnType}}{{^returnType}}null (empty response body){{/returnType}}
+{{#returnType}}{{#returnTypeIsPrimitive}}**{{returnType}}{{#nullableReturnType}}?{{/nullableReturnType}}**{{/returnTypeIsPrimitive}}{{^returnTypeIsPrimitive}}{{#generateModelDocs}}[**{{returnType}}{{#nullableReturnType}}?{{/nullableReturnType}}**]({{returnBaseType}}.md){{/generateModelDocs}}{{^generateModelDocs}}**{{returnType}}{{#nullableReturnType}}?{{/nullableReturnType}}**{{/generateModelDocs}}{{/returnTypeIsPrimitive}}{{/returnType}}{{^returnType}}null (empty response body){{/returnType}}
 
 ### Authorization
 

samples/client/others/kotlin-jvm-spring-3-restclient-nullable-return/docs/DefaultApi.md

@@ -50,7 +50,7 @@ No authorization required
 
 <a id="returnNullableString"></a>
 # **returnNullableString**
-> kotlin.String returnNullableString(pingRequest)
+> kotlin.String? returnNullableString(pingRequest)
 
 
 
@@ -81,7 +81,7 @@ try {
 
 ### Return type
 
-**kotlin.String**
+**kotlin.String?**
 
 ### Authorization