dsaControl module docs (prebid#5202)

Author: dgirardi

dev-docs/modules/dsaControl.md

@@ -0,0 +1,54 @@
+---
+layout: page_v2
+title: DSA Control Module
+display_name: DSA Control Module
+description: Digital Services Act bid validation  
+page_type: module
+module_code : dsaControl
+enable_download : true
+sidebarType : 1
+---
+
+# DSA Control Module
+{:.no_toc}
+
+* TOC
+  {:toc}
+
+## Overview
+
+The ORTB [DSA extension](https://github.com/InteractiveAdvertisingBureau/openrtb/blob/main/extensions/community_extensions/dsa_transparency.md) provides a method for publishers to request DSA transparency information, and for buyers to attach it to their bids. 
+This module adds validation for DSA information, discarding bids that do not match what was requested.
+
+## Usage
+
+With this module installed, validations are enabled by requesting DSA transparency information. For example:
+
+```javascript
+pbjs.setConfig({
+  ortb2: {
+      regs: {
+          ext: {
+              dsa: {
+                  dsarequired: 2,  
+                  pubrender: 0
+                  // ...
+              }
+          }
+      }
+  }
+})
+```
+
+This module will then enforce that:
+
+* all bids include DSA information, if required (`dsarequired` is either `2` or `3`);
+* all bids that provide DSA information use a compatible rendering method:
+  * if the request indicates that the publisher can't render (`pubrender` is `0`), then the advertiser must (`adrender` cannot be `0`);
+  * if it indicates that the publisher will render (`pubrender` is `2`), then the advertiser must not (`adrender` cannot be `1`).
+   
+Bids that fail the checks above are rejected with a console warning and removed from the auction.  
+
+## Further Reading
+
+* [DSA Transparency](https://github.com/InteractiveAdvertisingBureau/openrtb/blob/main/extensions/community_extensions/dsa_transparency.md)