feat(kafka): add sasl auth support

Signed-off-by: Andrew Thauer <athauer@wealthsimple.com>

plugins/kafka-backend/README.md

@@ -6,15 +6,15 @@ This is the backend part of the Kafka plugin. It responds to Kafka requests from
 
 This configures how to connect to the brokers in your Kafka cluster.
 
-### clientId
+### `clientId`
 
 The name of the client to use when connecting to the cluster.
 
-### brokers
+### `brokers`
 
 A list of the brokers' host names and ports to connect to.
 
-### SSL (optional)
+### `ssl` (optional)
 
 Configure TLS connection to the Kafka cluster. The options are passed directly to [tls.connect] and used to create the TLS secure context. Normally these would include `key` and `cert`.
 
@@ -24,7 +24,25 @@ Example:
 kafka:
   clientId: backstage
   clusters:
-    name: prod
-    brokers:
-      - localhost:9092
+    - name: prod
+      brokers:
+        - localhost:9092
+```
+
+### `sasl` (optional)
+
+Configure SASL authentication for the Kafka client.
+
+```yaml
+kafka:
+  clientId: backstage
+  clusters:
+    - name: prod
+      brokers:
+        - my-cluser:9092
+      ssl: true
+      sasl:
+        mechanism: plain # or 'scram-sha-256' or 'scram-sha-512'
+        username: my-username
+        password: my-password
 ```