ICRC-1: metadata constant or mutable? clarification needed

[timohanke]

We need some clarification in the spec regarding which metadata can change over time and which one is guaranteed to be constant.

For example, can decimals change? It is necessary for wallets to know if this can ever change or not. It seems natural that a token can "increase its precision" in the future. But since balances and transfer amounts are specified as nat-s in the smallest token unit that would not actually work. So I believe the answer is "no". If so then the spec should make this explicit.

Other metadata such as logo and fee can certainly change. With name and symbol it is not so clear.