Allow users to set temporal threshold for defining obs as unseen

[damianooldoni]

First of all: @niconoe, if you find a issue where this is already mentioned, please move this comment there. I searched, but didn't found although the problem here described is well known.

I got complaints from users about getting notifications of new (for the system) unseen observations from many years ago. Actually, the standard user of an early alert tool is not interested to old observations, even if they are new to the system and so to the users. So, they would like to not be notified, or at least having the possibility to choose.

During the meeting with some (super)users on Apr 20, we could agree on a strategy I woud like to share with you, @niconoe.

The idea is to give a user the possibility to set a temporal threshold in years while signing up or editing afterwards in Profile page.
Something like a checkbox followed by a space to fill in:

[x] Do not notify me about new imported observations older than [ 1 ] year(s)

Notice that this feature will avoid the annoying situation any new user encounters at the beginning of his/her experience with our tool, i.e. having almost ~60k unseen observations at once.

If a user enables this feature in Profile page afterwards, after clicking on "Save" button an "Are you sure?" pop-up should warn him that "n observations (e.g. 1000) observations will be flagged as "Seen" and buttons "Yes, I'm sure" and "Cancel". Similar to pop-up for account deletion.

@timadriaens, @bramdhondt: I would like your feedback on this as well.
@niconoe: what do you think about it?

[timadriaens]

Anything to make people see the trees for the forest. I actually wonder if we should just make that choice ourselves (e.g. only show data from the last year - this would of course depend on data publication frequency and probably there is an optimum in order to not lose too many data). I would perhaps be easier in terms of not having to do additional development and it would be simpler for the user.

Personally, as a user I tend to only look at the emails, and I rarely use the "Mark all observations as seen". Note this also sounds quite odd in English (also observed and seen is kinda the same), more correct would be "Mark all as viewed".

[damianooldoni]

Discussed with @niconoe yesterday: we both prefer to allow users to set up their own threshold in the past.
Maybe it's better to rewrite the negative sentence ("do not notify me") in a positive one something like:
[x] Notify me only about observations recorded during the last [ x ] year(s)

Use 1 year as default.

I moved the discussion about "Mark all as seen" vs "Mark all as viewed" in issue https://github.com/riparias/early-alert-webapp/issues/231.