Add instanceAge and projectIds docs.

docs/provisioners.md

@@ -177,6 +177,7 @@ In the ca.json, an AWS provisioner looks like:
     "accounts": ["1234567890"],
     "disableCustomSANs": false,
     "disableTrustOnFirstUse": false,
+    "instanceAge": "1h",
     "claims": {
         "maxTLSCertDuration": "2160h",
         "defaultTLSCertDuration": "2160h"
@@ -201,6 +202,9 @@ In the ca.json, an AWS provisioner looks like:
   granted per instance, but if the option is set to true this limit is not set
   and different tokens can be used to get different certificates.
 
+* `instanceAge` (optional): the maximum age of an instance to grant a
+  certificate. The instance age is a string using the duration format.
+
 * `claims` (optional): overwrites the default claims set in the authority, see
   the [JWK](#jwk) section for all the options.
 
@@ -217,8 +221,10 @@ In the ca.json, a GCP provisioner looks like:
     "type": "GCP",
     "name": "Google Cloud",
     "serviceAccounts": ["1234567890"],
+    "projectIDs": ["project-id"],
     "disableCustomSANs": false,
     "disableTrustOnFirstUse": false,
+    "instanceAge": "1h",
     "claims": {
         "maxTLSCertDuration": "2160h",
         "defaultTLSCertDuration": "2160h"
@@ -235,6 +241,9 @@ In the ca.json, a GCP provisioner looks like:
   allowed to use this provisioner. If none is specified, all service accounts
   will be valid.
 
+* `projectIDs` (optional): the list of project identifiers that are allowed to
+  use this provisioner. If non is specified all project will be valid.
+
 * `disableCustomSANs` (optional): by default custom SANs are valid, but if this
   option is set to true only the SANs available in the instance identity
   document will be valid, these are the DNS
@@ -245,6 +254,9 @@ In the ca.json, a GCP provisioner looks like:
   granted per instance, but if the option is set to true this limit is not set
   and different tokens can be used to get different certificates.
 
+* `instanceAge` (optional): the maximum age of an instance to grant a
+  certificate. The instance age is a string using the duration format.
+
 * `claims` (optional): overwrites the default claims set in the authority, see
   the [JWK](#jwk) section for all the options.