Rename: Prevent accidental change of the file extension

[tbsbdr]

Steps to reproduce

1. go to new design in https://web.owncloud.com/
2. select ownCloud Manual.pdf and choose "rename"
3. type "asd"
4. hit enter

Expected behaviour

file is renamed to asd.pdf and can still be opened via rightclick -> open with pdf viewer

Actual behaviour

file is renamed to asd and can not be opened with the pdf viewer

initial text-selection guides the user towards changing the file extension

Remedy

On rename, only the filename without extension should be pre text-selected

[phil-davis]

Note: the existing behavior of the oC10 classic webUI" is the same as the "Remedy" expected behavior here. So this issue will make web behave the same as the classic webUI.

It would be nice to have a test somewhere that checks this behavior - the rename test should type directly into the filed without clearing it, and verify that the file extension is preserved. Hopefully that is easy/possible with playwright.