Add azure kafka function sample

- Add sample project with Azure KafkaTrigger and Output Kakfa Bindings
 - Add README docs

 Resolves #836

spring-cloud-function-samples/function-sample-azure-kafka-trigger/README.md

@@ -0,0 +1,104 @@
+# Azure Function with Kafka Trigger & Output Binding
+
+Spring Cloud Function example for implementing an Azure functions with [KafkaTrigger](https://learn.microsoft.com/en-us/azure/azure-functions/functions-bindings-kafka-trigger?tabs=in-process%2Cconfluent&pivots=programming-language-java) and [Kafka Binding](https://learn.microsoft.com/en-us/azure/azure-functions/functions-bindings-kafka-output?tabs=in-process%2Cconfluent&pivots=programming-language-java) support.
+
+The Azure function is triggered by messages sent on the `trigger` topic and in turn calls the `uppercase` SCF with the trigger payload. The SCF capitalizes the input json value fields and sends the result to an output Kafka topic called: `output`.
+
+## Running Locally
+
+First start a Kafka server locally. 
+The `./src/main/resources/docker-compose-demo.yaml` helps to start locally Zookeeper, Kafka and Kafka UI.
+
+```
+docker-compose -f ./src/main/resources/docker-compose-demo.yaml up
+```
+You can reach the Kafka UI (Redpanda) dashboard on http://localhost:8080/topics
+
+![](./src/main/doc/kafka-ui-topics.png)
+
+The docker-compose pre-creates the `trigger` and `output` topics used by the function.
+
+Next build and run the Azure function:
+
+```
+./mvnw clean package
+./mvnw azure-functions:run
+```
+
+From the Kafka UI, got to the `trigger` topic view (http://localhost:8080/topics/trigger), select `Actions/Publish Message` and submit a new JSON message:
+```json
+{ "foo" : "bar"}
+```
+
+![](./src/main/doc/kafka-publish-message.png)
+
+
+Push the `Publish` button and let the function do its job and check the `output` topic (http://localhost:8080/topics/output) :
+
+![](./src/main/doc/output-topic.png)
+
+e.g.the `bar` is in uppercase:
+
+```json
+{ "foo" : "BAR"}
+```
+
+
+
+## Running on Azure (TODO: WIP)
+
+Make sure you are logged in your Azure account.
+```
+az login
+```
+
+Build and deploy
+
+```
+./mvnw clean package
+./mvnw azure-functions:deploy
+```
+
+## Implementation
+
+Configure the [Kafka extension](https://learn.microsoft.com/en-us/azure/azure-functions/functions-bindings-kafka?tabs=in-process%2Cportal&pivots=programming-language-java#hostjson-settings) in the `host.json` settings:
+
+```json
+{
+    "functionTimeout": "00:05:00",
+    "version": "2.0",
+    "extensions": {
+        "kafka": {
+            "maxBatchSize": 64,
+            "SubscriberIntervalInSeconds": 1,
+            "ExecutorChannelCapacity": 1,
+            "ChannelFullRetryIntervalInMs": 50
+        }
+    },
+    "extensionBundle": {
+        "id": "Microsoft.Azure.Functions.ExtensionBundle",
+        "version": "[3.3.0, 4.0.0)"
+    }
+}
+```
+
+Also to allow your functions to scale properly on the Premium plan when using Kafka triggers and bindings, you need to [enable runtime scale monitoring](https://learn.microsoft.com/en-us/azure/azure-functions/functions-bindings-kafka?tabs=in-process%2Cportal&pivots=programming-language-java#enable-runtime-scaling).
+
+
+## Notes
+
+* Disable the `spring-boot-maven-plugin` in favor of the `azure-functions-maven-plugin`.
+* Exclude the `org.springframework.boot:spring-boot-starter-logging` dependency from the `org.springframework.cloud:spring-cloud-function-adapter-azure`.
+* In `local.settings.json` set the local values for the `%BrokerList`, `%ConfluentCloudUsername%` and the `%TriggerKafkaTopic%` trigger and binding variables:
+
+```
+{
+	"IsEncrypted": false,
+	"Values": {
+...
+		"BrokerList": "localhost:9092",
+		"ConfluentCloudUsername": "test",
+		"TriggerKafkaTopic": "trigger"
+	}
+}
+```