support multipart/form-data (e.g. file uploads)

lib/codecs/corejson.js

@@ -73,6 +73,7 @@ function primitiveToNode (data, baseUrl) {
     const title = getString(data, 'title')
     const description = getString(data, 'description')
     const fieldsData = getArray(data, 'fields')
+    const encoding = getString(data, 'encoding') || 'application/json'
     var fields = []
     for (let idx = 0, len = fieldsData.length; idx < len; idx++) {
       let value = fieldsData[idx]
@@ -83,7 +84,7 @@ function primitiveToNode (data, baseUrl) {
       let field = new document.Field(name, required, location, fieldDescription)
       fields.push(field)
     }
-    return new document.Link(url, method, 'application/json', fields, title, description)
+    return new document.Link(url, method, encoding, fields, title, description)
   } else if (isObject) {
     // Object
     let content = {}

tests/codecs/corejson.js

@@ -81,6 +81,22 @@ describe('Test the CoreJSON Codec', function () {
     expect(node.fields).toEqual([new document.Field('foo', true)])
   })
 
+  it('should test decoding a link without declared encoding', function () {
+    const text = '{"_type": "link", "url": "http://example.com/", "fields": [{"name": "foo", "required": true}]}'
+    const node = codec.decode(text)
+    expect(node instanceof document.Link).toBeTruthy()
+    expect(node.fields).toEqual([new document.Field('foo', true)])
+    expect(node.encoding).toEqual('application/json')
+  })
+
+  it('should test decoding a link with declared encoding', function () {
+    const text = '{"_type": "link", "url": "http://example.com/", "encoding": "multipart/form-data", "fields": [{"name": "foo", "required": true}]}'
+    const node = codec.decode(text)
+    expect(node instanceof document.Link).toBeTruthy()
+    expect(node.fields).toEqual([new document.Field('foo', true)])
+    expect(node.encoding).toEqual('multipart/form-data')
+  })
+
   it('should test decoding a primitive', function () {
     const text = '123'
     const node = codec.decode(text)