Per-item price keys (price-id) (optional)

To allow multiple independent price entries for the same Minecraft Material (for example two different shop items that both use EXPERIENCE_BOTTLE), items may declare an optional price-id string in their configuration. When present, the plugin uses this price-id as the pricing key (and as the dynamic-pricing state key stored in shop-dynamic.yml) instead of the material name.

Notes:

• price-id is optional; if omitted the material name (e.g. DIAMOND, EXPERIENCE_BOTTLE) is used and pricing remains material-scoped (backwards compatible).
• price-id must be unique across your shop configuration if you want independent pricing/multipliers for two items that share the same material.
• Dynamic state (multipliers) are saved by price-id in shop-dynamic.yml when present; legacy material keys continue to be supported.

Example (category item):

my-exp-bottle-item:
material: EXPERIENCE_BOTTLE
price-id: exotic_exp_1   # optional unique key to separate pricing
buy: 10.0
sell: 5.0
dynamic-pricing:
  starting-multiplier: 1.0
  min-multiplier: 0.5
  max-multiplier: 3.0
  buy-change: 0.01
  sell-change: 0.01