Reward month occurence should be dynamic

[tenmoves]

Description

Please include a summary of the change and which issue is fixed. Please also include relevant motivation and context. List any dependencies that are required for this change.

Fixes #827

Type of change

Please delete options that are not relevant.

• Bug fix (non-breaking change which fixes an issue)

How Has This Been Tested?

Please describe the tests that you ran to verify your changes. Provide instructions so we can reproduce. Please also list any relevant details for your test configuration

• doctests
• manual

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published in downstream modules

[bchamagne]

If I understand correctly, the function Utils.number_of_reward_occurences_per_month() is working well and the issue is that it was called only at compile time.

Isn't it possible to just move it to runtime like this ?

defp number_of_reward_occurences_per_month() do 
    datetime = NaiveDateTime.utc_now()
    interval = Application.get_env(:archethic, RewardScheduler)[:interval]
    Utils.number_of_reward_occurences_per_month(interval, datetime)
end

[tenmoves]

no because in some cases depending on the interval it can take more than 1s to execute which is not acceptable