Fix deletion code and improve logging

[insacuri]

This PR was originally to add logging around the delete functionality. It expanded into tidying up the logic, adding a lot more logging and renaming some variables to make it more intuitive.

How to test

• Check out this branch locally
• Build and start it in sdx-compose
• cd <wherever your sdx-compose is>/pure-ftp-structure/EDC_Template_RAS
• touch filename.xlsx
• Check that the file is picked up and published when it looks for files. It won't delete it on the first pass because it needs to wait for confirmation.
• Check the file is deleted on the second pass.

[codecov[bot]]

Codecov Report

Merging #66 into master will decrease coverage by 0.16%. The diff coverage is 21.51%.

@@            Coverage Diff             @@
##           master      #66      +/-   ##
==========================================
- Coverage   55.97%   55.81%   -0.17%     
==========================================
  Files           8        8              
  Lines         611      611              
==========================================
- Hits          342      341       -1     
- Misses        269      270       +1

Impacted Files	Coverage Δ
app/test/localserver.py	33.84% <0%> (+0.51%)	:arrow_up:
app/publisher.py	37.5% <17.24%> (+0.3%)	:arrow_up:
app/main.py	36.6% <3.44%> (-1.15%)	:arrow_down:
app/ftpclient.py	92.85% <73.33%> (ø)	:arrow_up:

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