Add export-import example

examples/auth/export-import/cli/main.sh

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+#!/bin/bash
+
+set -euo pipefail
+
+NATS_URL=nats://localhost:4222
+
+cat <<- EOF > "server.conf"
+http_port: 8222
+jetstream: {}
+accounts: {
+  A: {
+    jetstream: true
+    users: [
+      {user: usera, password: usera}
+    ]
+    exports: [
+      # For account B to publish messages to the orders stream.
+      {service: "orders.*"}
+
+      # For account B to bind to the worker-B consumer on orders stream.
+      # This is specific to a push consumer with flow control enabled.
+      {stream: "worker-B.orders"}
+      {service: "\$JS.ACK.orders.worker-B.>"}
+      {service: "\$JS.FC.orders.worker-B.>"}
+    ]
+  }
+
+  B: {
+    jetstream: true
+    users: [
+      {user: userb, password: userb}
+    ]
+    imports: [
+      # Import ability to publish (request) messages into the orders stream.
+      {service: {account: A, subject: "orders.*"}}
+
+      # Import ability to subscribe to the target subject on worker-B consumer.
+      {stream: {account: A, subject: "worker-B.orders"}}
+      {service: {account: A, subject: "\$JS.ACK.orders.worker-B.>"}}
+      {service: {account: A, subject: "\$JS.FC.orders.worker-B.>"}}
+    ]
+  }
+}
+EOF
+
+# Start the server.
+echo 'Starting the server...'
+nats-server -c server.conf > /dev/null 2>&1 &
+
+nats context save A \
+  --user usera \
+  --password usera
+
+nats context save B \
+  --user userb \
+  --password userb
+
+# Add the stream in account A
+nats --context A stream add orders \
+  --subjects orders.* \
+  --retention=limits \
+  --storage=file \
+  --replicas=1 \
+  --discard=old \
+  --dupe-window=2m \
+  --max-age=-1 \
+  --max-msgs=-1 \
+  --max-bytes=-1 \
+  --max-msg-size=-1 \
+  --max-msgs-per-subject=-1 \
+  --max-consumers=-1 \
+  --allow-rollup \
+  --no-deny-delete \
+  --no-deny-purge
+
+# Confirm account B can publish to the stream.
+nats --context B req orders.1 "{}"
+
+# Report the stream.
+#nats --context A stream report
+
+# Create a consumer in account A whose API will be exported for B.
+# Specifically, this requires the `target` subject as a stream, and
+# the `$JS.ACK` subject to acknowledge messages.
+nats --context A consumer add orders worker-B \
+  --replicas 1 \
+  --deliver all \
+  --deliver-group "" \
+  --target worker-B.orders \
+  --ack explicit \
+  --replay instant \
+  --filter "" \
+  --heartbeat "2s" \
+  --flow-control \
+  --max-deliver="-1" \
+  --max-pending 128 \
+  --no-headers-only \
+  --backoff=none
+
+# Subscribe and consume one message from the imported subject
+# and ack it.
+nats --context B sub --ack worker-B.orders --count 1
+
+# Notice the consumer report shows no unprocessed messages.
+nats --context A consumer report orders

examples/auth/export-import/cli/server.conf

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+http_port: 8222
+jetstream: {}
+accounts: {
+  A: {
+    jetstream: true
+    users: [
+      {user: usera, password: usera}
+    ]
+    exports: [
+      {service: "orders.*"}
+      {service: "$JS.API.STREAM.INFO.orders"}
+      {stream: "worker-B"}
+    ]
+  }
+  B: {
+    jetstream: true
+    users: [
+      {user: userb, password: userb}
+    ]
+    imports: [
+      {service: {account: A, subject: "orders.*"}}
+      {service: {account: A, subject: "$JS.API.STREAM.INFO.orders"}}
+      {stream: {account: A, subject: "worker-B"}}
+    ]
+  }
+}

examples/auth/export-import/meta.yaml

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+title: Exports and Imports
+description: |-
+