APIv2 Create or Update contact allow ignoring Last activity

When programmatically updating or creating a contact via the API (e.g. POST /v2/contacts), the "Last activity" timestamp of the contact gets automatically set to "now".

This creates issues because updating background details (like plan names, custom fields, or tags) pollutes the actual user activity analytics.

Option or parameter in the API to allow updating contact details without modifying the "Last activity" timestamp would alleviate this.

This is important because it currently makes it impossible to know when the user was truly active last in the application when syncing data in the background.