File logging will fail due to invalid filename

Problem/Motivation

When enabling the file logging, it will not write any files. When having created the needed directories manually, it will actually fail, because it will use the description string as a filename practically as-is. The description for requests will be something like Response cache tags for GET /my/pages/url. The createFilename function will do some sanitization, but it does not take into account the slashes. Although the method's name might imply it does more to produce a valid filename, the description says: "Creates a full file path from a directory and filename. If a file with the specified name already exists, an alternative will be used." So, nothing there to imply it does any sanitization.

Steps to reproduce

• Enable the module
• Enable file logging
• Do a request, notice no log file is created
• Create a directory cache_debug/response in the private file location
• Do a request, notice how it fails

Proposed resolution

Sanitize the filename.

Remaining tasks

Create MR
Review
Merge

User interface changes

None.

API changes

None.

Data model changes

None.