Forbid to change extension with template

[tobiasKaminsky]

This will create otherwise a non-expected file, e.g template with ".md" is selected, but ".txt" is file name.

To test:

• select template or no
• see default extension
• change extension
  --> dialog cannot be confirmed

[alperozturk96]

When the user attempts to create a template for the first time, the dialog immediately displays a warning. The warning should not appear at the initial stage.

Instead, it would be more appropriate to show the warning only after the user attempts to modify the file extension.

[alperozturk96]

@kra-mo Do you think message is okay?

[github-actions]

APK file: https://www.kaminsky.me/nc-dev/android-artifacts/16523.apk



To test this change/fix you can simply download above APK file and install and test it in parallel to your existing Nextcloud app.

[github-actions]

Codacy

SpotBugs

Category	Base	New
Bad practice	42	42
Correctness	75	75
Dodgy code	256	256
Experimental	1	1
Internationalization	7	7
Malicious code vulnerability	2	2
Multithreaded correctness	34	34
Performance	44	44
Security	18	18
Total	479	479

[github-actions]

blue-Light-Screenshot test failed, but no output was generated. Maybe a preliminary stage failed.

[kra-mo]

@kra-mo Do you think message is okay?

Sure, it works fine :)