admin.controller.js

// pasting relevant bits

$scope.createPost = function() {
            $http({
                method: 'POST',
                url: '/db/createpost',
                data: $scope.postFormModel,
                headers: {'Content-Type': undefined},
            }).then(function successCallback(data) {
                console.log(data);
            }, function errorCallback(data) {
                console.log(data);
            });
        };
        
        // dropzone config
        $scope.dropzoneConfig = {
            'options': { // passed into the Dropzone constructor
                url: "/db/createpost",
                maxFilesize: 100,
                paramName: "uploadfile",
                maxThumbnailFilesize: 5,
                autoProcessQueue: false,
                maxFiles: 1

            },
            'eventHandlers': {
                'sending': function (file, xhr, formData) {
                },
                'success': function (file, response) {
                },
                'maxfilesexceeded': function(file){
                    this.removeFile(file);
                },
                'addedfile' : function(file){
                    $scope.postFormModel.flag = file.name;
                    $scope.$digest();
                }
            }
        };
        
// Form Fields
        $scope.postFormFields = [{
            type: 'input',
            key: 'postTitle',
            className: 'clearfix',
            templateOptions: {
                label: 'Title',
                required: true,
                className: 'col-md-6 col-xs-6'
            }
        }, {
            key: 'tags',
            type: 'ui-select-multiple',
            className: 'row margin20',
            templateOptions: {
                className: 'col-md-8 col-xs-6',
                optionsAttr: 'bs-options',
                ngOptions: 'option in to.options | filter: $select.search',
                label: 'Select tags',
                valueProp: 'id',
                labelProp: 'label',
                placeholder: 'Select tags for your content',
                options: testData, // Model containing tags
                tagTransform: $scope.tagTransform // the tag transform function needs to be a part of templateOptions
            }
        }, {
            type: 'textarea',
            key: 'content',
            className: 'clearfix',
            templateOptions: {
                rows: "12",
                label: 'Content',
                required: true,
                className: 'col-md-10 col-xs-12'
            }
        }, {
            type: 'textarea',
            key: 'excerpt',
            className: 'clearfix margin20',
            templateOptions: {
                rows: "3",
                label: 'Excerpt',
                required: true,
                className: 'col-md-10 col-xs-12'
            }
        },
        {
            key: 'flag',
            type: 'customInput',
            templateOptions: {
                label: 'flag',
                type: 'input',
                placeholder: 'Upload that image',
                required: true
            },
        },
        {
            type: 'repeatSection',
            key: 'citations',
            className: 'margin20',
            templateOptions: {
                btnText: 'Add another citation',
                fields: [{
                    fieldGroup: [{
                        type: 'input',
                        key: 'citationName',
                        className: 'formly-repeatSection',
                        templateOptions: {
                            className: 'col-md-10 col-xs-6',
                            label: 'Citation:',
                            required: false
                        }
                    }, {
                        type: 'input',
                        key: 'citationSource',
                        className: 'formly-repeatSection',
                        templateOptions: {
                            className: 'col-md-12 col-xs-6',
                            label: 'Source or hyperlink:',
                            placeholder: 'http://thisthatortheother.com/docs/papersonhysteria',
                            required: false
                        }
                    }]
                }]
            }
        }];
    }

admin.html

<form ng-submit="createPost()" name="form" novalidate enctype="multipart/form-data">
<formly-form model = "postFormModel" fields = "postFormFields"  form="form" class="admin">

  <button dropzone="dropzoneConfig" class="btn btn-primary">
        Drag and drop files here or click to upload
  </button>

  <div class="margin20">
    <button class="btn btn-primary" type="submit" ng-disabled="form.$invalid">Save Post</button>
  </div>
</formly-form>
</form>

server.js

var multer = require('multer');
var express = require('express');
var app = express();

app.post('/db/createpost', upload.single('flag'), function(req, res, next) {

console.log(req.files) // undefined

   postModel.create({
    title: req.body.postTitle,
    tags: req.body.tags,
    date_created: new Date(),
    date_updated: new Date(),
    attachment: req.body.attachedFile,
    is_draft: false,
    content: req.body.content,
    excerpt: req.body.excerpt,
    citation: req.body.citations,
   }, function(err, post){
    if(err){
        res.send(err);
    }

});

});