vault(api): fix nav to pki cert counters api (#1237)

* vault(api): fix nav to pki cert counters api

* vault(api): fix pki cert counters docs

Add Enterprise-only banner. Fix sample request and response payloads
to align with documented YYYY-MM format. Fix typo in first paragraph.

Author: gsantos-hc

content/vault/v1.21.x/content/api-docs/system/billing-pki-certificate-count.mdx renamed to content/vault/v1.21.x/content/api-docs/system/billing/certificates.mdx

@@ -5,10 +5,11 @@ description: >-
   Use the `/sys/billing/certificates` endpoint to fetch data about the number of PKI certificates issued by Vault.
 ---
 
-`# /sys/billing/certificates`
+# `/sys/billing/certificates`
 
-Use the `/sys/billing/certificates` endpoint to fetch data about the
-number of PKI certificates issued by Vault. for a cluster.
+@include '../partials/alerts/enterprise-only.mdx'
+
+Use the `/sys/billing/certificates` endpoint to fetch data about the number of PKI certificates issued by a Vault cluster.
 
 ## PKI Certificate Counts
 
@@ -24,7 +25,6 @@ By default, the endpoint returns data for the current billing period.
 - `start_time` `(string: "")` - The year and month indicating the first month of the
 query range in format `YYYY-MM`. The `start_time` is required if an `end_time` is provided.
 
-
 - `end_time` `(string: "")` - The year and month indicating the last month of the
 query range in format `YYYY-MM`. The `end_time` is required if a `start_time`
 is provided.
@@ -33,8 +33,8 @@ is provided.
 
 ```json
 {
-    "start_time": "2025-01-01",
-    "end_time": "2025-01-01"
+    "start_time": "2025-10",
+    "end_time": "2025-11"
 }
 ```
 
@@ -44,7 +44,7 @@ is provided.
 $ curl \
     --header "X-Vault-Token: ..." \
     --data @payload.json \
-    http://127.0.0.1:8200/v1/sys/billing/certificates
+    http://127.0.0.1:8200/v1/sys/billing/certificates?end_time=2025-11&start_time=2025-10
 ```
 
 ### Sample response
@@ -53,10 +53,17 @@ $ curl \
 {
     "months": [
         {
-            "timestamp": "2025-01-01",
             "counts": {
-                "issued_certificates": 123
-            }
+                "issued_certificates": 0
+            },
+            "error": "certificate counts not found for 2025-10",
+            "timestamp": "2025-10"
+        },
+        {
+            "counts": {
+                "issued_certificates": 2
+            },
+            "timestamp": "2025-11"
         }
     ]
 }

content/vault/v1.21.x/data/api-docs-nav-data.json

@@ -429,6 +429,10 @@
         "title": "<code>/sys/auth</code>",
         "path": "system/auth"
       },
+      {
+        "title": "<code>/sys/billing/certificates</code>",
+        "path": "system/billing/certificates"
+      },
       {
         "title": "<code>/sys/capabilities</code>",
         "path": "system/capabilities"
@@ -841,4 +845,4 @@
       }
     ]
   }
-]
+]