Drop experimental label for rebalanceSafeCommits (#1222)

RebalanceSafeCommits mode has been used extensively in production and
did not lead to any problems. I think it's time to remove the
experimental label.

docs/preventing-duplicates.md

@@ -0,0 +1,31 @@
+---
+id: preventing-duplicates
+title: "Preventing duplicates"
+---
+
+In zio-kafka processing of records runs asynchronously with partition management. This brings substantial performance
+advantages but causes some records to be consumed and processed _twice_ when a rebalance occurs. To prevent this,
+since version 2.7.1 zio-kafka supports a new mode in which we prevent duplicates due to rebalances. You can enable it
+as follows:
+
+```scala
+import zio.*
+import zio.kafka.consumer.ConsumerSettings
+
+val consumerSettings: ConsumerSettings =
+  ConsumerSettings(List("localhost:9092"))
+    .withGroupId("group")
+    .withRebalanceSafeCommits(true)       // enable rebalance-safe-commits mode
+    .withMaxRebalanceDuration(30.seconds) // defaults to 3 minutes
+```
+
+With rebalance-safe-commits mode enabled, rebalances are held up for up to max-rebalance-duration to wait for pending
+commits to be completed. Once pending commits are completed, it is safe for another consumer in the group to take over
+a partition.
+
+For this to work correctly, your program must process a chunk of records within max-rebalance-duration. The clock
+starts the moment the chunk is pushed into the stream and ends when the commits for these records complete.
+
+For more information see the scaladocs in `ConsumerSettings`, read the description of
+[pull request #1098](https://github.com/zio/zio-kafka/pull/1098) that introduced this feature, or watch the presentation
+[Making ZIO-Kafka Safer And Faster](https://www.youtube.com/watch?v=MJoRwEyyVxM). The relevant part starts at 10:24.

docs/sidebars.js

@@ -10,6 +10,7 @@ const sidebars = {
         "example-of-consuming-producing-and-committing-offsets",
         "partition-assignment-and-offset-retrieval",
         "consumer-tuning",
+        "preventing-duplicates",
         "sharing-consumer",
         "serialization-and-deserialization",
         "writing-tests"

zio-kafka/src/main/scala/zio/kafka/consumer/ConsumerSettings.scala

@@ -190,8 +190,6 @@ final case class ConsumerSettings(
     copy(restartStreamOnRebalancing = value)
 
   /**
-   * NOTE: 'rebalanceSafeCommits' is an EXPERIMENTAL feature. It is not recommended for production use yet.
-   *
    * @param value
    *   Whether to hold up a rebalance until all offsets of consumed messages have been committed. The default is
    *   `false`, but the recommended value is `true` as it prevents duplicate messages.
@@ -224,8 +222,6 @@ final case class ConsumerSettings(
     copy(rebalanceSafeCommits = value)
 
   /**
-   * NOTE: 'rebalanceSafeCommits' is an EXPERIMENTAL feature. It is not recommended for production use yet.
-   *
    * @param value
    *   Maximum time spent in the rebalance callback when `rebalanceSafeCommits` is enabled.
    *