Make NameAwareAttributes#remove Case-insensitive

Closes gh-548

core/src/main/java/org/springframework/ldap/core/NameAwareAttributes.java

@@ -99,7 +99,7 @@ public Attribute put(Attribute attr) {
     @Override
     public Attribute remove(String attrID) {
         Assert.hasLength(attrID, "Attribute ID must not be empty");
-        return attributes.remove(attrID);
+        return attributes.remove(attrID.toLowerCase());
     }
 
     @Override

core/src/test/java/org/springframework/ldap/core/NameAwareAttributesTest.java

@@ -0,0 +1,25 @@
+package org.springframework.ldap.core;
+
+import org.junit.Test;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+public class NameAwareAttributesTest {
+    // gh-548
+    @Test
+    public void removeWhenDifferentCaseThenRemoves() {
+        NameAwareAttributes attributes = new NameAwareAttributes();
+        attributes.put("myID", "value");
+        attributes.put("myOtherID", "othervalue");
+        assertThat(attributes.size()).isEqualTo(2);
+        assertThat(attributes.get("myid").get()).isEqualTo("value");
+        assertThat(attributes.get("myID").get()).isEqualTo("value");
+
+        attributes.remove("myid");
+        assertThat(attributes.get("myID")).isNull();
+        assertThat(attributes.size()).isEqualTo(1);
+
+        attributes.remove("myOtherID");
+        assertThat(attributes.size()).isEqualTo(0);
+    }
+}