[debug-toolbar/display_source_code/security] add security mechanism to only read whitelisted files
Closes #17256791
CSS Coding Standards
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(Draft, to be continued)
:Naming: camelCase
Indentation rules
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- 2 spaces before properties
- no space before ":", one space after
- only one space between values of the same property
Documentation
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Please keep rules semantically linked grouped together, with a comment about
what they are for.
Recommendation
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- Try to use existing classes rather than introduce new ones
- Keep things as simple as possible while in the framework
- Think about later customization by application
- Avoid introducing a new CSS file for a few lines of CSS, at least while the
framework doesn't include packing functionalities