PIG 26 - Roadmap for v2.0

[registerrier]

Description

This pull request is the draft for the PIG presenting the roadmap to v2.0.
For now it summarizes a google doc that was discussed among lead dev and project manager.

Dear reviewer

[adonath]

One thing we have also discussed in the past is the Plotter API. Could be added too, however we already have enough things to do...

[adonath]

Smaller projects would include adding TimeMapAxis to support center coordinates and a MapAxis supporting intervals.

[codecov]

Codecov Report

Merging #4388 (b95c804) into main (ec9df57) will increase coverage by 0.08%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main    #4388      +/-   ##
==========================================
+ Coverage   94.83%   94.92%   +0.08%     
==========================================
  Files         216      218       +2     
  Lines       30501    30880     +379     
==========================================
+ Hits        28925    29312     +387     
+ Misses       1576     1568       -8     

Impacted Files	Coverage Δ
gammapy/irf/background.py	97.02% <ø> (+0.01%)	⬆️
gammapy/irf/edisp/map.py	96.47% <ø> (ø)
gammapy/data/data_store.py	94.46% <100.00%> (+0.03%)	⬆️
gammapy/irf/core.py	93.11% <100.00%> (ø)
gammapy/irf/io.py	92.42% <100.00%> (ø)

... and 55 files with indirect coverage changes

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[bkhelifi]

Dear all,
I am wondering whether some interface to the VO TAP server could be useful for the future. This could be a new feature to our DataSTore.
The library pyvo could be used at least. A small survey might be desirable before choosing the right underlying library to implement new functions with the Gammapy API style.

[bkhelifi]

The roadmap for the v2.0 should be in PIG 27, as PIG 26 is the Model Priors API.
One should maybe publish it, now, the draft being started in March, 2023...