@Haarolean What's the deprecation policy in Kafka UI?

Should this be done within the 0.5 milestone or one version after? @joschi in 0.6 :)  @joschi wanna nuke it? 
Drop deprecated protobuf single file property
        TODO drop deprecated protobuf single file property

_Originally posted by @Haarolean in https://github.com/provectus/kafka-ui/pull/2874#discussion_r1015295797_
      
.gitignore kafka-ui-api/src/main/java/com/provectus/kafka/ui/serdes/builtin/ProtobufFileSerde.java
.gitignore kafka-ui-api/src/main/java/com/provectus/kafka/ui/serdes/builtin/ProtobufFileSerde.java
kafka-ui-api/src/test/java/com/provectus/kafka/ui/serdes/builtin/ProtobufFileSerdeTest.java
diff --git a/.gitignore b/.gitignore
index 55b770349f8..a12e7753760 100644
--- a/.gitignore
+++ b/.gitignore
@@ -31,6 +31,9 @@ build/
 .vscode/
 /kafka-ui-api/app/node
 
+### SDKMAN ###
+.sdkmanrc
+
 .DS_Store
 *.code-workspace
 
diff --git a/kafka-ui-api/src/main/java/com/provectus/kafka/ui/serdes/builtin/ProtobufFileSerde.java b/kafka-ui-api/src/main/java/com/provectus/kafka/ui/serdes/builtin/ProtobufFileSerde.java
index 8a4c28a320a..05809e26912 100644
--- a/kafka-ui-api/src/main/java/com/provectus/kafka/ui/serdes/builtin/ProtobufFileSerde.java
+++ b/kafka-ui-api/src/main/java/com/provectus/kafka/ui/serdes/builtin/ProtobufFileSerde.java
@@ -50,7 +50,6 @@
 import java.io.ByteArrayInputStream;
 import java.nio.file.Files;
 import java.nio.file.Path;
-import java.nio.file.Paths;
 import java.util.Collection;
 import java.util.HashMap;
 import java.util.List;
@@ -204,17 +203,13 @@ record Configuration(@Nullable Descriptor defaultMessageDescriptor,
                        Map<String, Descriptor> keyMessageDescriptorMap) {
 
     static boolean canBeAutoConfigured(PropertyResolver kafkaClusterProperties) {
-      Optional<String> protobufFile = kafkaClusterProperties.getProperty("protobufFile", String.class);
       Optional<List<String>> protobufFiles = kafkaClusterProperties.getListProperty("protobufFiles", String.class);
       Optional<String> protobufFilesDir = kafkaClusterProperties.getProperty("protobufFilesDir", String.class);
-      return protobufFilesDir.isPresent()
-          || protobufFile.isPresent()
-          || protobufFiles.filter(files -> !files.isEmpty()).isPresent();
+      return protobufFilesDir.isPresent() || protobufFiles.filter(files -> !files.isEmpty()).isPresent();
     }
 
     static Configuration create(PropertyResolver properties) {
       var protobufSchemas = loadSchemas(
-          properties.getProperty("protobufFile", String.class),
           properties.getListProperty("protobufFiles", String.class),
           properties.getProperty("protobufFilesDir", String.class)
       );
@@ -272,12 +267,11 @@ private static Map<String, Descriptor> populateDescriptors(Map<String, Descripto
     }
 
     @VisibleForTesting
-    static Map<Path, ProtobufSchema> loadSchemas(Optional<String> protobufFile,
-                                                 Optional<List<String>> protobufFiles,
+    static Map<Path, ProtobufSchema> loadSchemas(Optional<List<String>> protobufFiles,
                                                  Optional<String> protobufFilesDir) {
       if (protobufFilesDir.isPresent()) {
-        if (protobufFile.isPresent() || protobufFiles.isPresent()) {
-          log.warn("protobufFile and protobufFiles properties will be ignored, since protobufFilesDir provided");
+        if (protobufFiles.isPresent()) {
+          log.warn("protobufFiles properties will be ignored, since protobufFilesDir provided");
         }
         List<ProtoFile> loadedFiles = new ProtoSchemaLoader(protobufFilesDir.get()).load();
         Map<String, ProtoFileElement> allPaths = loadedFiles.stream()
@@ -288,10 +282,8 @@ static Map<Path, ProtobufSchema> loadSchemas(Optional<String> protobufFile,
                 f -> new ProtobufSchema(f.toElement(), List.of(), allPaths)));
       }
       //Supporting for backward-compatibility. Normally, protobufFilesDir setting should be used
-      return Stream.concat(
-              protobufFile.stream(),
-              protobufFiles.stream().flatMap(Collection::stream)
-          )
+      return protobufFiles.stream()
+          .flatMap(Collection::stream)
           .distinct()
           .map(Path::of)
           .collect(Collectors.toMap(path -> path, path -> new ProtobufSchema(readFileAsString(path))));

diff --git a/kafka-ui-api/src/test/java/com/provectus/kafka/ui/serdes/builtin/ProtobufFileSerdeTest.java b/kafka-ui-api/src/test/java/com/provectus/kafka/ui/serdes/builtin/ProtobufFileSerdeTest.java
index ab99df74de6..1b295dc77a4 100644
--- a/kafka-ui-api/src/test/java/com/provectus/kafka/ui/serdes/builtin/ProtobufFileSerdeTest.java
+++ b/kafka-ui-api/src/test/java/com/provectus/kafka/ui/serdes/builtin/ProtobufFileSerdeTest.java
@@ -47,7 +47,6 @@ class ProtobufFileSerdeTest {
   @BeforeEach
   void setUp() throws Exception {
     Map<Path, ProtobufSchema> files = ProtobufFileSerde.Configuration.loadSchemas(
-        Optional.empty(),
         Optional.empty(),
         Optional.of(protoFilesDir())
     );
@@ -107,15 +106,6 @@ void canBeAutoConfiguredReturnsNoProtoPropertiesProvided() {
           .isFalse();
     }
 
-    @Test
-    void canBeAutoConfiguredReturnsTrueIfNoProtoFileHasBeenProvided() {
-      PropertyResolver resolver = mock(PropertyResolver.class);
-      when(resolver.getProperty("protobufFile", String.class))
-          .thenReturn(Optional.of("file.proto"));
-      assertThat(Configuration.canBeAutoConfigured(resolver))
-          .isTrue();
-    }
-
     @Test
     void canBeAutoConfiguredReturnsTrueIfProtoFilesHasBeenProvided() {
       PropertyResolver resolver = mock(PropertyResolver.class);
@@ -193,13 +183,10 @@ void unknownSchemaAsTopicSchemaForKeyThrowsException() {
     @Test
     void createConfigureFillsDescriptorMappingsWhenProtoFilesListProvided() throws Exception {
       PropertyResolver resolver = mock(PropertyResolver.class);
-      when(resolver.getProperty("protobufFile", String.class))
-          .thenReturn(Optional.of(
-              ResourceUtils.getFile("classpath:protobuf-serde/sensor.proto").getPath()));
-
       when(resolver.getListProperty("protobufFiles", String.class))
           .thenReturn(Optional.of(
               List.of(
+                  ResourceUtils.getFile("classpath:protobuf-serde/sensor.proto").getPath(),
                   ResourceUtils.getFile("classpath:protobuf-serde/address-book.proto").getPath())));
 
       when(resolver.getProperty("protobufMessageName", String.class))
