#1413: Handle "+" character in file paths

[baxter-huntington]

URLDecoder.decode applies the application/x-www-form-urlencoded MIME format, which includes converting "+" characters to space characters. If a path contains "+" characters, upon re-encoding, they will be converted to %20 instead of %2b, yielding a different file path than we started with.

We handle this by converting "+" to "%2b" before decoding to ensure that it is preserved across the round trip.

Resolves: #1413

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 86.17%. Comparing base (a1a50c0) to head (ca1aff0).

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1414      +/-   ##
==========================================
- Coverage   86.24%   86.17%   -0.07%     
==========================================
  Files         112      112              
  Lines       10289    10289              
  Branches     4056     4056              
==========================================
- Hits         8874     8867       -7     
- Misses        809      814       +5     
- Partials      606      608       +2     

see 4 files with indirect coverage changes

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[Thrameos]

Seems very reasonable, though we will likely need to improve it a bit before inclusion.

1. Is '+' the only problem character or do we need more substitutions?

AI states this is likely needed.

/ Centralized protection for characters that have special meaning in 
// x-www-form-urlencoded but are literal characters in file paths.
private static String prepareForDecoding(String input) {
    return input.replace("+", "%2b")
                .replace("&", "%26")
                .replace("=", "%3D")
                .replace("#", "%23");
}

2. We need a doc/CHANGELOG entry so we track the improvement
3. We need something in test/jpypetest that exercises the bug.

I can generate those for you when I have development cycles free. Or you can add it and we can skip straight to review.

Thanks for the contribution!

[baxter-huntington]

@Thrameos I appreciate the quick look and response 😃 I'd be happy to address those items. I should have some time to get to them tomorrow.