Summary

Configuring syntax highlighting for custom file extensions does not take effect

Steps to Reproduce

1. In bitbucket.properties add an entry for extension e.g. for .csproj syntax.highlighter.application/xml.extensions=csproj
2. Restart Bitbucket server
3. Add a file with .csproj extension and some XML content
4. Browse the file

Expected Results

Content is highlighted as https://codemirror.net/mode/xml/index.html

Actual Results

Content is not highlighted

Note: This issue has also been seen to affect standard file extension detection, where the wrong syntax highlighting may be seen to be applied to standard file extensions (e.g. Objective-C may have Mathematica highlighting incorrectly applied)