feat kafka: document task processors and allow their customization

Tests: протестировано CI
commit_hash:1363ff2b1222d56624aa9e6f7708859d8b50f480

Author: apolukhin

kafka/src/kafka/consumer_component.cpp

@@ -18,6 +18,14 @@ USERVER_NAMESPACE_BEGIN
 
 namespace kafka {
 
+namespace {
+
+std::string TaskProcessorName(std::string_view name, const components::ComponentConfig& config) {
+    return config[name].As<std::string>(name);
+}
+
+}  // namespace
+
 ConsumerComponent::ConsumerComponent(
     const components::ComponentConfig& config,
     const components::ComponentContext& context
@@ -26,9 +34,9 @@ ConsumerComponent::ConsumerComponent(
       consumer_(
           config.Name(),
           config["topics"].As<std::vector<std::string>>(),
-          context.GetTaskProcessor("consumer-task-processor"),
-          context.GetTaskProcessor("consumer-blocking-task-processor"),
-          context.GetTaskProcessor("main-task-processor"),
+          context.GetTaskProcessor(TaskProcessorName("consumer-task-processor", config)),
+          context.GetTaskProcessor(TaskProcessorName("consumer-blocking-task-processor", config)),
+          context.GetTaskProcessor(config["task-processor"].As<std::string>("main-task-processor")),
           config.As<impl::ConsumerConfiguration>(),
           context.FindComponent<components::Secdist>()
               .Get()

kafka/src/kafka/consumer_component.yaml

@@ -2,6 +2,18 @@ type: object
 description: Kafka consumer component
 additionalProperties: false
 properties:
+    task-processor:
+        type: string
+        description: the name of the TaskProcessor to invoke callbacks
+        default: main-task-processor
+    consumer-task-processor:
+        type: string
+        description: TaskProcessor for message batches polling. Feel free to use 'main-task-processor'.
+        default: consumer-task-processor
+    consumer-blocking-task-processor:
+        type: string
+        description: TaskProcessor for consumer blocking operations. Feel free to use 'fs-task-processor'.
+        default: consumer-blocking-task-processor
     group_id:
         type: string
         description: |