Add unprotect_terms to the list of modifiers for bracketed patterns

[k3KAW8Pnf7mkmdSMPHz27]

The bracketed patterns for renaming files don't translate fields to Unicode, so if there are protected terms ({In} {CDMA}) the brackets will be translated to underscore, (_In_ _CDMA_) which cannot be removed by the regex modifier (which respects protected terms).

This PR adds the already existing UnprotectTermsFormatter to the list of available modifiers, which can be used through the key unprotect_terms.

The motivation for adding it is https://discourse.jabref.org/t/filename-format-pattern-novice-user/2872 .

• Change in CHANGELOG.md described in a way that is understandable for the average user (if applicable)
• Tests created for changes (if applicable)
• Manually tested changed features in running JabRef (always required)
• Screenshots added in PR description (for UI changes)
• Checked documentation: Is the information available and up to date? If not created an issue at https://github.com/JabRef/user-documentation/issues or, even better, submitted a pull request to the documentation repository.

[Siedlerchr]

In addtion to remove_braces we also have add_braces. Not sure if this should be added as well?

[k3KAW8Pnf7mkmdSMPHz27]

In addtion to remove_braces we also have add_braces. Not sure if this should be added as well?

I am not sure either 😛
I can't think of a use-case for it, but that doesn't mean it doesn't exist or won't exist in the future. Perhaps add it if/when it is needed?

[Siedlerchr]

Yeah, if we come up with a use case we can always add it later