Add text transformation pipes (uppercase, lowercase, capitalize) support in translations

[allandiegoasilva]

Clear and concise description of the problem

Currently, nestjs-i18n allows interpolation of variables (e.g. {{field}}) but doesn’t provide built-in support for simple text transformations such as uppercase, lowercase, or capitalize within translation files.

This makes it harder to handle case-sensitive requirements directly in the translation strings (e.g., UI titles, field labels) and forces developers to apply manual post-processing after calling i18n.translate().

Suggested solution

Example translation file:

 {
    "greeting": "Hello, {{name}}!"
  }

Expected usage in code:

await this.i18n.translate('shared.greeting', {
  lang: 'en',
  args: { name: 'john doe' },
 transform: "uppercase"
});

// Potentially with modifier → "Hello, JOHN DOE!"

Alternative

Maybe can add uppsercase on translate file.

 {
    "greeting": "Hello, {{name | uppercase}}!"
  }

Additional context

No response

Validations

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• Read the Contributing Guide.
• Check that there isn't already an issue that request the same feature to avoid creating a duplicate.

[toonvanstrijp]

I think allowing the text transformations via the translate file would be best. If you have a custom loader which fetches them from the database this would still work.