(DOCSP-45304) adds api documentation for taking an on demand snapshot-v8.0-backport (633) (#758)

# Backport

This will backport the following commits from `master` to `v8.0`:
- [(DOCSP-45304) adds page to
toc](10gen/docs-ops-manager#633)
- [(DOCSP-45304) fixes build
errors](10gen/docs-ops-manager#633)
- [(DOCSP-45304) eliminating a redundant
line](10gen/docs-ops-manager#633)
- [(DOCSP-45304) copy
feedback](10gen/docs-ops-manager#633)
- [(DOCSP-45304) adds api docs for taking an on-demand
snapshot](10gen/docs-ops-manager#633)
- [(DOCSP-45304) re initiating
build](10gen/docs-ops-manager#633)
- [(DOCSP-45304) fixes build
error](10gen/docs-ops-manager#633)

<!--- Backport version: 9.6.3 -->

### Questions ?
Please refer to the [Backport tool
documentation](https://github.com/sorenlouv/backport)

---------

Co-authored-by: Carrie Kim <[email protected]>

Author: davidhou17

source/includes/extracts-api-toc-snapshots.yaml

@@ -9,8 +9,8 @@ content: |
      Get One (Cluster) </reference/api/snapshots/get-one-snapshot-for-one-cluster>
      Change Expiry </reference/api/snapshots/change-expiry-for-one-snapshot>
      Remove One </reference/api/snapshots/remove-one-snapshot-from-one-cluster>
+     Create One On-Demand (Cluster) </reference/api/snapshots/take-an-on-demand-snapshot>
      Get All (Config Server) </reference/api/snapshots/get-all-snapshots-for-config-server>
      Get One (Config Server) </reference/api/snapshots/get-one-snapshot-for-config-server>
 
-
 ...

source/reference/api/snapshots.txt

@@ -55,6 +55,10 @@ The following lists the endpoints available for snapshots.
        :gold:`IMPORTANT:` To delete a snapshot, you must issue the
        request from an IP address on your user account's
        :ref:`access list <access-list-for-api-operations>`.
+   
+   * - POST
+     - :doc:`/groups/{groupId}/clusters/{clusterId}/snapshots/onDemandSnapshot </reference/api/snapshots/take-an-on-demand-snapshot>`
+     - Create one on-demand snapshot for a cluster.
 
 .. important:: Deprecated when using MongoDB 3.4
 

source/reference/api/snapshots/take-an-on-demand-snapshot.txt

@@ -1,6 +1,6 @@
-==========================
-Take an On-Demand Snapshot
-==========================
+============================
+Create an On-Demand Snapshot
+============================
 
 .. default-domain:: mongodb
 
@@ -51,17 +51,21 @@ Request Path Parameters
 Request Query Parameters
 ~~~~~~~~~~~~~~~~~~~~~~~~
 
-The following query parameters are optional:
-
 .. list-table::
    :widths: 20 14 11 45 10
    :header-rows: 1
    :stub-columns: 1
 
+   * - Name
+     - Type
+     - Necessity
+     - Description
+     - Example
+
    * - retentionDays
      - number
      - Required
-     - Integer that indicates the number of days the the on-demand 
+     - Integer that indicates the number of days the on-demand 
        snapshot will be retained. Must be greater than 0.
      - ``15``
 
@@ -102,14 +106,14 @@ Example Response
 ----------------
 
 Response Header
-+++++++++++++++
+~~~~~~~~~~~~~~~~
 
 .. include:: /includes/api/api-headers/401.rst
 
 .. include:: /includes/api/api-headers/200.rst
 
 Response Body
-+++++++++++++
+~~~~~~~~~~~~~~~~
 
 .. code-block:: json