Add example of getting started with nsc + nats account-server (#71)

* Update nas_conf.md

* Add more details to the NATS Account Server setup

nats-tools/nas/nas_conf.md

@@ -156,3 +156,75 @@ Let's take a look at the configuration options:
 | `cert` | filepath to the certificate. |
 | `cert` | filepath to the certificate key. |
 
+## Example Setup
+
+Provided a setup with 4 accounts, one of them a system account, this example shows how to set up the account server by:
+
+* adding the account server to the operator
+* configuring the account server
+* push the accounts to the account server
+* configure a `nats-server` to make use of the account server
+* test the setup
+
+```sh
+$ export NKEYS_PATH=$(pwd)/nsc/nkeys
+$ export NSC_HOME=$(pwd)/nsc/accounts
+
+# Setup script that creates a few sample accounts and a system account
+$ curl -sSL https://nats-io.github.io/k8s/setup/nsc-setup.sh | sh
+
+$ nsc list accounts
+╭─────────────────────────────────────────────────────────────────╮
+│                            Accounts                             │
+├──────┬──────────────────────────────────────────────────────────┤
+│ Name │ Public Key                                               │
+├──────┼──────────────────────────────────────────────────────────┤
+│ A    │ AA6LOQIZRKEAC5FUGLMZHAXERZRQFAFQOO7YC6ZMQ325BYUAEPDUEIV5 │
+│ B    │ ACPD2M7QFV33HPPY563PI7C664LXG2YVWXQBB6EAHDXZR7EK7L52AWUG │
+│ STAN │ ABD4DPO745A5U2JKPWCI7LFGW4UCTN5LPUXDA5BCMXEYWLCU7J346NGU │
+│ SYS  │ AB25DCM6BL5SDWYR45F65MSVOVXATN64AZXGI7IGS3IXBPWWDB4FIR2H │
+╰──────┴──────────────────────────────────────────────────────────╯
+
+# Add the endpoint for the account server to which accounts can be published
+$ nsc edit operator --account-jwt-server-url http://localhost:9090/jwt/v1/ --service-url nats://localhost:4222
+
+# Generate account server config that references the operator jwt
+$ echo '
+operatorjwtpath: "./nsc/accounts/nats/KO/KO.jwt"
+
+http {
+    port: 9090
+}
+' > nats-account-server.conf
+
+# Start the account server
+$ nats-account-server -c nats-account-server.conf &
+
+# Upload the local accounts in the nsc directory structure
+$ nsc push -A
+
+# Generate the NATS Server config that points to the account server
+$ echo '
+operator: "./nsc/accounts/nats/KO/KO.jwt"
+resolver: URL(http://localhost:9090/jwt/v1/accounts/)
+system_account: AB25DCM6BL5SDWYR45F65MSVOVXATN64AZXGI7IGS3IXBPWWDB4FIR2H
+' > nats-server.conf
+
+# Start the NATS Server in trusted operator mode
+$ nats-server -c nats-server.conf &
+
+# Try to subscribe on account without permissions, this should fail
+$ nats-sub -creds nsc/nkeys/creds/KO/A/test.creds foo
+nats: Permissions Violation for Subscription to "foo"
+
+# Subscribe then publish to subject should work on 'test' since enough permissions
+$ nats-sub -creds nsc/nkeys/creds/KO/A/test.creds test &
+Listening on [test]
+
+# Published message on 'test' subject would be received by started subscriber above
+$ nats-pub -creds nsc/nkeys/creds/KO/A/test.creds test foo &
+Listening on [test]
+
+# Subscribe using the system account user credentials can receive all system events
+$ nats-sub -creds nsc/nkeys/creds/KO/SYS/sys.creds '>'
+```