App Role guide update.

Documents issuing both client and server certificates. WIF relies on
client certificates.

Server example documents an example of internal Web service using an
autorenewing internal certificate.

vault_configure.sh

@@ -44,6 +44,19 @@ vault write pki_int/roles/wif-client \
     max_ttl=8760h \
     no_store=true
 
+# Create a role that issues server authentication certificates
+vault write pki_int/roles/web-server \
+    allow_any_name=true \
+    enforce_hostnames=true \
+    server_flag=true \
+    client_flag=false \
+    key_type=rsa \
+    key_bits=4096 \
+    key_usage=DigitalSignature,KeyEncipherment \
+    ttl=8760h \
+    max_ttl=8760h \
+    no_store=true
+
 # Export the CA certificates
 vault read -field=certificate pki/cert/ca > ca_cert.pem
 vault read -field=certificate pki_int/cert/ca > issuing_ca_cert.pem