Remove Codec.encodeNull(int) as we don't require each codec to implement null encoding with a given OID

[#378]

Author: mp911de

src/main/java/io/r2dbc/postgresql/codec/AbstractCodec.java

@@ -98,7 +98,6 @@ public EncodedParameter encode(Object value, int dataType) {
         return doEncode((T) value, PostgresqlObjectId.valueOf(dataType));
     }
 
-    @Override
     public EncodedParameter encodeNull(int dataType) {
         return new EncodedParameter(Format.FORMAT_BINARY, dataType, NULL_VALUE);
     }

src/main/java/io/r2dbc/postgresql/codec/Codec.java

@@ -98,15 +98,6 @@ public interface Codec<T> {
      */
     EncodedParameter encodeNull();
 
-    /**
-     * Encode a {@code null} value using the given {@code dataType}.
-     *
-     * @param dataType the Postgres OID
-     * @return the encoded {@code null} value
-     * @since 0.9
-     */
-    EncodedParameter encodeNull(int dataType);
-
     /**
      * Returns the Java {@link Class type} of this codec.
      *

src/main/java/io/r2dbc/postgresql/codec/EnumCodec.java

@@ -105,8 +105,7 @@ public EncodedParameter encodeNull() {
         return encodeNull(this.oid);
     }
 
-    @Override
-    public EncodedParameter encodeNull(int dataType) {
+    private EncodedParameter encodeNull(int dataType) {
         return new EncodedParameter(Format.FORMAT_BINARY, dataType, NULL_VALUE);
     }
 

src/main/java/io/r2dbc/postgresql/codec/HStoreCodec.java

@@ -227,8 +227,7 @@ public EncodedParameter encodeNull() {
         return encodeNull(this.oid);
     }
 
-    @Override
-    public EncodedParameter encodeNull(int dataType) {
+    private EncodedParameter encodeNull(int dataType) {
         return new EncodedParameter(Format.FORMAT_BINARY, dataType, NULL_VALUE);
     }
 

src/test/java/io/r2dbc/postgresql/CodecExtensionIntegrationTests.java

@@ -138,8 +138,7 @@ public EncodedParameter encodeNull() {
             return null;
         }
 
-        @Override
-        public EncodedParameter encodeNull(int dataType) {
+        private EncodedParameter encodeNull(int dataType) {
             return null;
         }
 

src/test/java/io/r2dbc/postgresql/codec/DefaultCodecsUnitTests.java

@@ -181,8 +181,7 @@ public EncodedParameter encodeNull() {
             return null;
         }
 
-        @Override
-        public EncodedParameter encodeNull(int dataType) {
+        private EncodedParameter encodeNull(int dataType) {
             return null;
         }