Document aggregation functionality

Author: thekid

ChangeLog.md

@@ -3,6 +3,8 @@ MongoDB for XP Framework ChangeLog
 
 ## ?.?.? / ????-??-??
 
+## 0.5.0 / 2020-08-08
+
 * Added new methods `Collection::distinct()` and `Collection::count()`
   (@thekid)
 * Added new method `Collection::aggregate()` to perform aggregations, see

README.md

@@ -60,13 +60,22 @@ $result= $c->collection('test.products')->update($inc->where(['name' => 'Test'])
 Console::writeLine('>> ', $result);
 ```
 
-
 Authentication
 --------------
 To authenticate, pass username and password via the connection string, e.g. `mongodb://user:pass@localhost`. The authentication source defaults to *admin* but can be set by supplying a path, e.g. `mongodb://user:pass@localhost/test`.
 
 Currently, *SCRAM-SHA-1* is the only supported authentication mechanism.
 
+Aggregation
+-----------
+The `Collection` class also features aggregation methods:
+
+* `count($filter= [])`
+* `distinct($key, $filter= [])`
+* `aggregate($pipeline)`
+
+See https://docs.mongodb.com/manual/reference/command/nav-aggregation/
+
 Type mapping
 ------------
 All builtin types are mapped to their BSON equivalents. In addition, the following type mappings are used: