Allow user uploads

[WillieCubed]

The user should be able to upload a post to the back end for processing.

The app will send an HTTP POST request to the endpoint /posts with the parameters described in the API docs. Once a response is received, it should store the data in its state management system in Flutter, ready to be displayed.

[WillieCubed]

I'm going to go ahead and reopen this because there's currently no code in the repo to formally close this issue.

Normally, we'd use a pull request to do a code review and get back then. merge the feature into the development branch. Once a PR associated with an issue is merged, the issue automatically closes. In addition, I configured the Kanban board to automatically move issues to "Complete" once they've closed. TL;DR: Pull requests will automagically close everything.

At tonight's meeting, I'll talk about GitHub more, and we'll set up our feaure branches and combined project structure for the front and back end.