Added range validation to copy existing configuration

KAFKA-22 / KAFKA-65

Author: rozza

src/main/java/com/mongodb/kafka/connect/source/MongoSourceConfig.java

@@ -230,6 +230,7 @@ public Map<String, ConfigValue> validateAll(final Map<String, String> props) {
         configDef.define(COPY_EXISTING_MAX_THREADS_CONFIG,
                 Type.INT,
                 COPY_EXISTING_MAX_THREADS_DEFAULT,
+                ConfigDef.Range.atLeast(1),
                 Importance.MEDIUM,
                 COPY_EXISTING_MAX_THREADS_DOC,
                 group,
@@ -240,6 +241,7 @@ public Map<String, ConfigValue> validateAll(final Map<String, String> props) {
         configDef.define(COPY_EXISTING_QUEUE_SIZE_CONFIG,
                 Type.INT,
                 COPY_EXISTING_QUEUE_SIZE_DEFAULT,
+                ConfigDef.Range.atLeast(1),
                 Importance.MEDIUM,
                 COPY_EXISTING_QUEUE_SIZE_DOC,
                 group,