Display a warning regarding Week numbers in case of different standards for a specific year

Is your feature request related to a problem? Please describe.

3 standards are described in Wikipedia regarding week numbers: https://en.wikipedia.org/wiki/ISO_week_date

Let's imagine we want to plan a meeting with someone in Zimbabwe during the summer. If we want to plan the week number 26 for instance. Depending on the current year, this number will not be the same week for the person in Zimbabwe and someone in Europe. In 2021, week 26 correspond to June 28, 2021 to July 4, 2021 for France. For Zimbabwe, this maps to June 20, 2021 to June 26, 2021

Describe the solution you'd like

We would like to know directly in the agenda if the week number is the same everywhere or not. With Jordan, we had a first idea. If we select the option to display the week number and the week number is not the same in the 3 standards, then we could display a warning on top of the agenda after the year. If we pass the mouse over the warning then we could display a message explaining that the week number can be different in some countries.

Describe alternatives you've considered

We have not considered any alternative yet.

Additional context

We didn't find any related issue in the GitHub repository or nothing proposing this feature on the Nextcloud forum. Do you think it could be a good feature for Nextcloud Calendar? We are 2 people motivated to implement it.

No files, tests, or entry points are named. Start by reviewing the calendar agenda and its week-number display, then verify how the three standards differ for a selected year and how a warning could be presented. Done means the agenda clearly warns users when week numbers are not consistent across standards.