Describe the solution you'd like
Being able to set vein data for the player entity and have it add to item-sourced data.

  "vein_data": {
    "chargeCap": 0,
    "chargeRate": 0.0
  }

Why is this feature needed
To allow a background regen/cap to be set.

Describe alternatives you've considered
Having it as an option in the pmmo-server.toml file.

Having it as an option in the server toml is the better approach.

[Vein Settings]
#how much vein players gain passively.  is additive with items
passive_charge_rate = 0.01
#the vein cap players maintain when no items are involved
passive_vein_cap = 5

This is easier than the datapack part.