DOCSP-19443 add an arraySort expression v5.2 (#147)

* DOCSP-19443 Add an array sort expression

* First example

* Upstream merge conflict

* First pass

* TOC links

* Fake

* Undo fake

* Table alignment

* Staging Tweaks

* Review suggestions

* Review comments

* Review comments

Author: Dave

source/includes/extracts-agg-operators.yaml

@@ -234,6 +234,10 @@ content: |
 
         - Returns a subset of an array.
 
+      * - :expression:`$sortArray`
+
+        - Sorts the elements of an array.
+
       * - :expression:`$zip`
 
         - Merge two arrays together.

source/reference/operator/aggregation.txt

@@ -953,6 +953,8 @@ Alphabetical Listing of Expression Operators
 
      - Returns a subset of an array.
 
+   * - :expression:`$sortArray`
+     - Sorts an array based on its elements.
 
    * - :expression:`$split`
 
@@ -1301,6 +1303,7 @@ Alphabetical Listing of Expression Operators
    /reference/operator/aggregation/sin
    /reference/operator/aggregation/sinh
    /reference/operator/aggregation/slice
+   /reference/operator/aggregation/sortArray
    /reference/operator/aggregation/split
    /reference/operator/aggregation/sqrt
    /reference/operator/aggregation/stdDevPop

source/reference/operator/aggregation/setUnion.txt

@@ -67,6 +67,11 @@ Behavior
 
           [ [ "a", "b" ], "b", "a" ]
 
+.. note::
+
+   Starting in MongoDB 5.2, the sort order for :expression:`$setUnion`
+   is undefined. To sort an array, refer to :expression:`$sortArray`.
+
 Example
 -------
 
@@ -109,3 +114,4 @@ The operation returns the following results:
    { "A": [ "red", "blue" ], "B": [ [ "red", "blue" ] ], "allValues": [ "blue", "red", [ "red", "blue" ] ] }
    { "A": [ ], "B": [ ], "allValues": [ ] }
    { "A": [ ], "B": [ "red" ], "allValues": [ "red" ] }
+