[BUG] 0.7.0 PO Import tools issues

[eeintech]

Describe the bug

There are multiple issues with the Purchase Order import tool:

1. When user selects a file, file name is shown twice

2. On step 2, the file column names are missing from the view

3. Still on step 2, the two actions buttons are "Previous Step" and "Upload File", but file was already uploaded

4. Attempt to go to step 3 clicking on "Upload File" results in automatic error

Steps to Reproduce

Steps to reproduce the behavior:

1. Click on an existing and pending purchase order
2. Click on "Upload File" button
3. Follow the form

Version Information
InvenTree-Version: 0.7.0
Django Version: 3.2.13
Commit Hash: 044315a
Commit Date: 2022-05-24
Database: postgresql
Debug-Mode: False
Deployed using Docker: False

Deployment Method: Bare Metal

[SchrodingersGat]

I think we should make the leap and migrate the Purchase Order importer to the API importer (as is used for BOM importing)

Ref: #3097

[SchrodingersGat]

There is too much work required here to fix this, as we will be overhauling the entire import tool in #3101

[Geekly]

Is there a workaround for this, or is importing for a PO just not going to work?

[eeintech]

@matmair Could there be a workaround before 1.0.0 / #3101 gets around?

[matmair]

For sure; one could simply add the importer improvements discussed in the issue and close it. 1.0 is basically a big wishlist that signals that the issue would be nice and a lot of work.
I have in the back of my mind that @SchrodingersGat wanted to tackle it this year but I could be wrong about that.