FINERACT-2316: Localize interest rate chart slab validation

- Add localized validation messages for overlap and gap errors in interest rate chart slabs
- Use DataValidatorBuilder with resource/parameter context for clean error codes
- Add unit tests for validation error codes and arguments
- Add German translations for validation messages

fineract-provider/src/main/resources/messages.properties

@@ -0,0 +1,22 @@
+#
+# Licensed to the Apache Software Foundation (ASF) under one
+# or more contributor license agreements. See the NOTICE file
+# distributed with this work for additional information
+# regarding copyright ownership. The ASF licenses this file
+# to you under the Apache License, Version 2.0 (the
+# "License"); you may not use this file except in compliance
+# with the License. You may obtain a copy of the License at
+#
+# http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing,
+# software distributed under the License is distributed on an
+# "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+# KIND, either express or implied. See the License for the
+# specific language governing permissions and limitations
+# under the License.
+#
+
+# Interest Rate Chart validation messages
+validation.msg.savings.interestRateChart.slabs.overlap=There is an overlap between slabs {0} and {1}.
+validation.msg.savings.interestRateChart.slabs.gap=There is a gap between slabs {0} and {1}.

fineract-provider/src/main/resources/messages_de.properties

@@ -0,0 +1,22 @@
+#
+# Licensed to the Apache Software Foundation (ASF) under one
+# or more contributor license agreements. See the NOTICE file
+# distributed with this work for additional information
+# regarding copyright ownership. The ASF licenses this file
+# to you under the Apache License, Version 2.0 (the
+# "License"); you may not use this file except in compliance
+# with the License. You may obtain a copy of the License at
+#
+# http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing,
+# software distributed under the License is distributed on an
+# "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+# KIND, either express or implied. See the License for the
+# specific language governing permissions and limitations
+# under the License.
+#
+
+# Interest Rate Chart validation messages
+validation.msg.savings.interestRateChart.slabs.overlap=Es gibt eine Überlappung zwischen Segmenten {0} und {1}.
+validation.msg.savings.interestRateChart.slabs.gap=Es gibt eine Lücke zwischen Segmenten {0} und {1}.