Object parameters cannot be read from a file

[lbergnehr]

Describe the bug

According to

porter/docs/content/docs/bundle/manifest/_index.md

Line 182 in f61648f

porter install --param config=./config.json

,
an object parameter should, much like the file type parameter, be able to be
taken from a file directly when specified using the --param option in e.g.
porter install.

To Reproduce

Steps to reproduce the behavior:

1. Use this porter.yaml:

   schemaType: Bundle
   schemaVersion: 1.0.1
   name: porter-repro
   version: 0.1.0
   description: "An example Porter configuration"
   registry: "localhost:5000"
   
   # Declare and optionally configure the mixins used by the bundle
   mixins:
     - exec
   
   parameters:
     - name: object_parameter
       type: object
       path: /cnab/app/object_parameter.json
   
   # Define the steps that should execute when the bundle is installed
   install:
     - exec:
         description: "Install Hello World"
         command: echo
         arguments:
           - install ${ bundle.parameters.object_parameter }
   
   # Define the steps that should execute when the bundle is upgraded
   upgrade:
     - exec:
         description: "World 2.0"
         command: ./helpers.sh
         arguments:
           - upgrade
   
   # Define the steps that should execute when the bundle is uninstalled
   uninstall:
     - exec:
         description: "Uninstall Hello World"
         command: ./helpers.sh
         arguments:
           - uninstall

2. Put the following in object_parameter.json:

   {
     "key": "value"
   }

3. Run porter install --param object_parameter=./object_parameter.json

4. Observe the error:

   unable to convert parameter's object_parameter value ./object_parameter.json to the destination parameter type object: could not unmarshal value ./object_parameter.json into a json object: invalid character '.' looking for beginning of value
   

Expected behavior

The file should be read and marshalled into the object parameter
representation if the parameter given in the --param option is pointing to a
file.

Version

porter v1.2.0 (45c17c15)