fixed edge case where different cased headers would override instead of combine

Author: Wicpar

build.gradle

@@ -4,7 +4,7 @@ plugins {
 }
 
 group 'com.github.papsign'
-version '0.2-beta.17-SNAPSHOT'
+version '0.2-beta.18-SNAPSHOT'
 
 repositories {
     mavenCentral()

src/main/kotlin/com/papsign/ktor/openapigen/parameters/handlers/ModularParameterHandler.kt

@@ -29,7 +29,7 @@ class ModularParameterHandler<T>(val parsers: Map<KParameter, Builder<*>>, val c
 
     override fun parse(parameters: Parameters, headers: Headers): T {
         return constructor.callBy(parsers.mapValues {
-            val value = it.value.build(it.key.name.toString(), it.key.remapOpenAPINames(parameters.toMap() + headers.toMap().mapKeys { it.key.toLowerCase() }))
+            val value = it.value.build(it.key.name.toString(), it.key.remapOpenAPINames(parameters.toMap() + headers.toMap().entries.groupBy { it.key.toLowerCase() }.mapValues { it.value.flatMap { it.value } }))
             if (value != null || it.key.type.isMarkedNullable) {
                 value
             } else {