docs: refine comments on multipart params (#295)

chore(internal): make multipart assertions more robust
chore(internal): remove unnecessary `assertNotNull` calls

Author: stainless-app[bot]

onebusaway-sdk-kotlin-core/src/main/kotlin/org/onebusaway/core/http/HttpRequestBodies.kt

@@ -5,7 +5,6 @@ package org.onebusaway.core.http
 import com.fasterxml.jackson.databind.JsonNode
 import com.fasterxml.jackson.databind.json.JsonMapper
 import com.fasterxml.jackson.databind.node.JsonNodeType
-import java.io.ByteArrayInputStream
 import java.io.InputStream
 import java.io.OutputStream
 import org.apache.hc.client5.http.entity.mime.MultipartEntityBuilder
@@ -69,12 +68,12 @@ internal fun multipartFormData(
             when (node.nodeType) {
                 JsonNodeType.MISSING,
                 JsonNodeType.NULL -> emptySequence()
-                JsonNodeType.BINARY -> sequenceOf(name to ByteArrayInputStream(node.binaryValue()))
-                JsonNodeType.STRING -> sequenceOf(name to node.textValue().toInputStream())
+                JsonNodeType.BINARY -> sequenceOf(name to node.binaryValue().inputStream())
+                JsonNodeType.STRING -> sequenceOf(name to node.textValue().inputStream())
                 JsonNodeType.BOOLEAN ->
-                    sequenceOf(name to node.booleanValue().toString().toInputStream())
+                    sequenceOf(name to node.booleanValue().toString().inputStream())
                 JsonNodeType.NUMBER ->
-                    sequenceOf(name to node.numberValue().toString().toInputStream())
+                    sequenceOf(name to node.numberValue().toString().inputStream())
                 JsonNodeType.ARRAY ->
                     node.elements().asSequence().flatMap { element -> serializePart(name, element) }
                 JsonNodeType.OBJECT ->
@@ -88,7 +87,7 @@ internal fun multipartFormData(
                     )
             }
 
-        private fun String.toInputStream(): InputStream = ByteArrayInputStream(toByteArray())
+        private fun String.inputStream(): InputStream = toByteArray().inputStream()
 
         override fun writeTo(outputStream: OutputStream) = entity.writeTo(outputStream)