Add request validation

Author: marcoscaceres

index.html

@@ -696,6 +696,30 @@ <h3>
           |request| to a JSON string. [=exception/throw|Re-throw=] any
           [=exception=].
           </li>
+          <li>If |requests|'s {{DigitalCredentialGetRequest/protocol}} is not
+          allowed by the user agent, [=exception/throw=] a
+          {{NotSupportedError}} {{DOMException}}.
+          </li>
+          <li>If the [=digital credential/exchange protocol=] defines an IDL
+          [=dictionary=] for [=converted to an idl value|conversion=]:
+            <ol>
+              <li>Let |request| be |requests|'s
+              {{DigitalCredentialGetRequest/data}} [=converted to an idl
+              value|converted=] to a |dictionary|. [=exception/throw|Rethrow=]
+              any exceptions.
+              </li>
+            </ol>
+          </li>
+          <li>Otherwise, let |request| be |requests|'s
+          {{DigitalCredentialGetRequest/data}}.
+          </li>
+          <li>Validate |request| against any validation rules set forth in the
+          corresponding [=registry/link|Specification=]. If any of |request|'s
+          members are invalid, [=exception/throw=] a {{TypeError}}.
+          </li>
+          <li>Set [=list/item=] at |providers|'s |n| index's
+          {{DigitalCredentialGetRequest/data}} to |request|
+          </li>
         </ol>
       </li>
       <li>