Add support for bitbucket server 6.6.2

[BosAtWork]

Issue #, if available:
JSON format of webhook of bitbucket server 6.6.2 is not supported and slighly different than normal Bitbucket.

Description of changes:
Added support for bitbucket server 6.6.2 as the json is slighly different and the branch name is in a different path.

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Sample json that bitbucket server 6.6.2 sends as hook

{
   "eventKey":"repo:refs_changed",
   "date":"2020-01-14T16:30:45+0100",
   "actor":{
      "name":"****",
      "emailAddress":"****",
      "id":8361,
      "displayName":"****",
      "active":true,
      "slug":"****",
      "type":"NORMAL",
      "links":{
         "self":[
            {
               "href":"****"
            }
         ]
      }
   },
   "repository":{
      "slug":"****",
      "id":2659,
      "name":"****",
      "scmId":"git",
      "state":"AVAILABLE",
      "statusMessage":"Available",
      "forkable":false,
      "project":{
         "key":"****",
         "id":2264,
         "name":"****",
         "description":"****",
         "public":false,
         "type":"NORMAL",
         "links":{
            "self":[
               {
                  "href":"****"
               }
            ]
         }
      },
      "public":false,
      "links":{
         "clone":[
            {
               "href":"****.git",
               "name":"http"
            },
            {
               "href":"ssh://git@****.git",
               "name":"ssh"
            }
         ],
         "self":[
            {
               "href":"https://****/browse"
            }
         ]
      }
   },
   "changes":[
      {
         "ref":{
            "id":"refs/heads/hotfix/transfer-should-be-checked",
            "displayId":"hotfix/transfer-should-be-checked",
            "type":"BRANCH"
         },
         "refId":"refs/heads/hotfix/transfer-should-be-checked",
         "fromHash":"0000000000000000000000000000000000000000",
         "toHash":"4a24622fd85f304770079a8b4dbf9566ea1928c5",
         "type":"ADD"
      }
   ]
}

[BosAtWork]

@jaymccon Is there any chance this might be looked at. At the moment our organization has to have extra step in the deployment guidelines to fix the lambda code manually after deploying this quickstart.