Issue with Localized Placeholder Texts on English Pages

[yesil]

In some locales, there are pages that remain in English, e.g., see (1). On these pages, localized placeholder keys are still being loaded, resulting in a mix of English content and localized placeholder text. This issue can be observed at (1), where the page itself is in English, but the placeholder texts are localized.

Potential Solutions

1. Disable Localized Placeholders for Non-Localized Pages:
   One approach could be to ensure that Milo does not load localized placeholder keys if the page itself is not localized. However, implementing this change could potentially break existing pages that rely on the current behavior.

2. Page Metadata Configuration:
   Another option is to allow authors to control this behavior by adding a specific metadata configuration to the page. This way, authors can explicitly decide whether or not to load localized placeholders, depending on the content of the page.

3. Other Options?
   Are there alternative approaches we should consider to address this issue?

References

1. Example EN page with mixed localization
   
2. localized page

[mokimo]

+1 to the Page Metadata option. These pages are special cases and we should indicate that those are special. I wonder if there are any other features that could face similar issues?

Localized links should still be okay, MEP maybe? Where they'd switch out english parts for localized parts?

It's currently overall not a use-case we support, I'm not sure if there are enough of those pages to warrant exceptions or a big strategy either 🤔

A metadata flag to start out with for placeholders would be a good option.

[yesil]

Fragments are physical english copies so their paths do not need to be transformed.
i'll ask the initial reporter of the issue to fill a JIRA via their PM for Milo core :)