Fix missing file extension validation on Data Files page

[jtimpe]

Thank you for taking the time to let us know about the issue you found. The basic rule for bug reporting is that
something isn't working the way one would expect it to work. Please provide us with the information requested
below and we will look at it as soon as we are able.

Description

In this comment, Eric points out that the (OG) Data Files page is no longer performing the file extension validation when a file is selected.

e.g.,

Action Taken

• Navigate to the Data Files page. Search, then select a not-allowed file type (png or jpeg, for example)

What I expected to see

When selecting a file, the extension should be checked against allowed extensions, like this example from the FRA Data Files page

What I did see

• No file extension error when selecting the file (precheck)
• Data file is allowed to be submitted (but then fails at the backend with a file extension error)

Other Helpful Information

• URL of the page I was on:
• Browser and version:
• Operating System: ( Windows | MacOS X | Linux | Other )
• Is the issue repeatable?: ( yes | no | don't know )
• Has the issue occurred more than once?:

[lhuxraft]

@jtimpe to confirm if this issue is happening in staging? Also update screenshots

[jtimpe]

issue is present in staging @lhuxraft @ADPennington

[ADPennington]

issue is present in staging @lhuxraft @ADPennington

Thank you @jtimpe. Can we prioritize this? pen-testing is in-progress. @lhuxraft

[ADPennington]

helpful error message when attempting to submit png @jtimpe

[jtimpe]

helpful error message when attempting to submit png @jtimpe

right - the backend extension check is still functioning. the frontend one is not, however

[lhuxraft]

issue is present in staging @lhuxraft @ADPennington

Thank you @jtimpe. Can we prioritize this? pen-testing is in-progress. @lhuxraft

For sure - I'll shortlist for inclusion in the next sprint