Add UI helpers for when a (non-permanent) feature has been open for longer than x days

[matthewelwell]

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

I want to be able to see how long a feature has existed.

Describe the solution you'd like.

I think we can add a few things to help here:

1. Show a UI hint on each feature if it has been more than x days since it was created
2. Show a statistic above the features which provides the total number of features that were created more than x days ago
3. Clicking this statistic (or similar) should filter the list of features for those that were created more than x days ago

Describe alternatives you've considered

N/a

Additional context

No response

[matthewelwell]

From an API perspective, we need to provide:

1. An option to filter the list of features based on 'created date is less than X'
2. Some meta statistics on the features in a given project. I'm wondering if this can be added as an extra attribute in the response to GET /projects/:id/features/. e.g. alongside "results" in the paged response we could add a "meta" attribute which then provides statistics about all the features in the project. Alternatively, we could create a new /statistics endpoint which would provide this data.