doc: add cert template api usage

docs/documentation/platform/pki/certificate-templates.mdx

@@ -55,4 +55,61 @@ In the following steps, we explore how to issue a X.509 certificate using a cert
   </Step>
 </Steps>
   </Tab>
+  <Tab title="API">
+    <Steps>
+        <Step title="Creating the certificate template">
+            To create a certificate template, make an API request to the [Create Certificate Template](/api-reference/endpoints/certificate-templates/create) API endpoint.
+
+            ### Sample request
+
+            ```bash Request
+            curl --request POST \
+              --url https://app.infisical.com/api/v1/pki/certificate-templates \
+              --header 'Content-Type: application/json' \
+              --data '{
+              "caId": "<string>",
+              "pkiCollectionId": "<string>",
+              "name": "<string>",
+              "commonName": "<string>",
+              "subjectAlternativeName": "<string>",
+              "ttl": "<string>"
+            }'
+            ```
+
+            ### Sample response
+
+            ```bash Response
+            {
+              "id": "3c90c3cc-0d44-4b50-8888-8dd25736052a",
+              "caId": "3c90c3cc-0d44-4b50-8888-8dd25736052a",
+              "name": "<string>",
+              "commonName": "<string>",
+              "subjectAlternativeName": "<string>",
+              "pkiCollectionId": "3c90c3cc-0d44-4b50-8888-8dd25736052a",
+              "ttl": "<string>",
+              "projectId": "<string>",
+              "caName": "<string>"
+            }
+            ```
+        </Step>
+        <Step title="Using the certificate template">
+          To use the certificate template, attach the certificate template ID when invoking the API endpoint for [issuing](/api-reference/endpoints/certificates/issue-certificate) or [signing](/api-reference/endpoints/certificates/sign-certificate) new certificates.
+
+          ### Sample request
+
+            ```bash Request
+            curl --request POST \
+              --url https://app.infisical.com/api/v1/pki/certificates/issue-certificate \
+              --header 'Content-Type: application/json' \
+              --data '{
+              "certificateTemplateId": "<string>",
+              "friendlyName": "<string>",
+              "commonName": "<string>",
+              ...
+            }'
+            ```
+        </Step>
+    </Steps>
+
+  </Tab>
 </Tabs>