Add basic filestack webhook.

closes #1542

Generalize event.

Add doc.

Update default config.

Add filestack to the list of plugins.

Check that video conversion event returns 400.

Update the readme.

Update the changelog.

plugins/inputs/webhooks/filestack/filestack_webhooks_events_json_test.go

@@ -0,0 +1,110 @@
+package filestack
+
+func DialogOpenJSON() string {
+	return `{
+	  "action": "fp.dialog",
+	  "timestamp": 1435584646,
+	  "id": 102,
+	  "text": {
+	    "mimetypes": ["*/*"],
+	    "iframe": false,
+	    "language": "en",
+	    "id": "1435584650723",
+	    "mobile": false,
+	    "app":{
+	       "upsell": "false",
+	       "apikey": "YOUR_API_KEY",
+	       "customization":{
+	          "saveas_subheader": "Save it down to your local device or onto the Cloud",
+	          "folder_subheader": "Choose a folder to share with this application",
+	          "open_subheader": "Choose from the files on your local device or the ones you have online",
+	          "folder_header": "Select a folder",
+	          "help_text": "",
+	          "saveas_header": "Save your file",
+	          "open_header": "Upload a file"
+	       }
+	    },
+	    "dialogType": "open",
+	    "auth": false,
+	    "welcome_header": "Upload a file",
+	    "welcome_subheader": "Choose from the files on your local device or the ones you have online",
+	    "help_text": "",
+	    "recent_path": "/",
+	    "extensions": null,
+	    "maxSize": 0,
+	    "signature": null,
+	    "policy": null,
+	    "custom_providers": "imgur,cloudapp",
+	    "intra": false
+	  }
+	}`
+}
+
+func UploadJSON() string {
+	return `{
+	   "action":"fp.upload",
+	   "timestamp":1443444905,
+	   "id":100946,
+	   "text":{
+	      "url":"https://www.filestackapi.com/api/file/WAunDTTqQfCNWwUUyf6n",
+	      "client":"Facebook",
+	      "type":"image/jpeg",
+	      "filename":"1579337399020824.jpg",
+	      "size":139154
+	   }
+	}`
+}
+
+func VideoConversionJSON() string {
+	return `{
+	   "status":"completed",
+	   "message":"Done",
+	   "data":{
+	      "thumb":"https://cdn.filestackcontent.com/f1e8V88QDuxzOvtOAq1W",
+	      "thumb100x100":"https://process.filestackapi.com/AhTgLagciQByzXpFGRI0Az/resize=w:100,h:100,f:crop/output=f:jpg,q:66/https://cdn.filestackcontent.com/f1e8V88QDuxzOvtOAq1W",
+	      "thumb200x200":"https://process.filestackapi.com/AhTgLagciQByzXpFGRI0Az/resize=w:200,h:200,f:crop/output=f:jpg,q:66/https://cdn.filestackcontent.com/f1e8V88QDuxzOvtOAq1W",
+	      "thumb300x300":"https://process.filestackapi.com/AhTgLagciQByzXpFGRI0Az/resize=w:300,h:300,f:crop/output=f:jpg,q:66/https://cdn.filestackcontent.com/f1e8V88QDuxzOvtOAq1W",
+	      "url":"https://cdn.filestackcontent.com/VgvFVdvvTkml0WXPIoGn"
+	   },
+	   "metadata":{
+	      "result":{
+	         "audio_channels":2,
+	         "audio_codec":"vorbis",
+	         "audio_sample_rate":44100,
+	         "created_at":"2015/12/21 20:45:19 +0000",
+	         "duration":10587,
+	         "encoding_progress":100,
+	         "encoding_time":8,
+	         "extname":".webm",
+	         "file_size":293459,
+	         "fps":24,
+	         "height":260,
+	         "mime_type":"video/webm",
+	         "started_encoding_at":"2015/12/21 20:45:22 +0000",
+	         "updated_at":"2015/12/21 20:45:32 +0000",
+	         "video_bitrate":221,
+	         "video_codec":"vp8",
+	         "width":300
+	      },
+	      "source":{
+	         "audio_bitrate":125,
+	         "audio_channels":2,
+	         "audio_codec":"aac",
+	         "audio_sample_rate":44100,
+	         "created_at":"2015/12/21 20:45:19 +0000",
+	         "duration":10564,
+	         "extname":".mp4",
+	         "file_size":875797,
+	         "fps":24,
+	         "height":360,
+	         "mime_type":"video/mp4",
+	         "updated_at":"2015/12/21 20:45:32 +0000",
+	         "video_bitrate":196,
+	         "video_codec":"h264",
+	         "width":480
+	      }
+	   },
+	   "timestamp":"1453850583",
+	   "uuid":"638311d89d2bc849563a674a45809b7c"
+	}`
+}