Allow optional AWS credentials

Author: blootsvoets

src/main/java/org/radarbase/output/config/RestructureConfig.kt

@@ -350,18 +350,21 @@ data class S3Config(
     /** URL to reach object store at. */
     val endpoint: String,
     /** Access token for writing data with. */
-    val accessToken: String,
+    val accessToken: String?,
     /** Secret key belonging to access token. */
-    val secretKey: String,
+    val secretKey: String?,
     /** Bucket name. */
     val bucket: String,
     /** If no endOffset is in the filename, read it from object tags. */
     val endOffsetFromTags: Boolean = false,
 ) {
-    fun createS3Client(): MinioClient = MinioClient.Builder()
-        .endpoint(endpoint)
-        .credentials(accessToken, secretKey)
-        .build()
+
+    fun createS3Client(): MinioClient = MinioClient.Builder().apply {
+        endpoint(endpoint)
+        if (!accessToken.isNullOrBlank() && !secretKey.isNullOrBlank()) {
+            credentials(accessToken, secretKey)
+        }
+    }.build()
 
     fun withEnv(prefix: String): S3Config = this
         .copyEnv("${prefix}S3_ACCESS_TOKEN") { copy(accessToken = it) }