SL-281: Added support for insertDocument

[farhatahmad]

fixes #941

Description

Adds support for the insertDocument BigBlueButton Api call: https://docs.bigbluebutton.org/development/api#insertdocument

Testing Steps

Assuming you have a meetingID=random-195645, you can run the following command:

curl -s -X POST "http://localhost:4000/bigbluebutton/api/insertDocument?meetingID=random-195645&checksum=7cf422cc7e509f5ac578617e2d057058ce2f091a" --header "Content-Type: application/xml" --data '<modules>
   <module name="presentation">
        <document current="true" downloadable="true" url="{link to download the presentation}" filename="sample.pdf"/>
        <document removable="false" name="sample.pdf"> 

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        </document>
   </module>
</modules>'

Screenshots (if appropriate):