Fix an erroneus claim regarding auditing the current supply of tokens where...

Fix an erroneus claim regarding auditing the current supply of tokens where the supply hasn't been fixed yet

We can only verify the "fixedness" using the SPV sub-DAG approach, and only when fixedness is verified can we can verify the actual "official" supply from that subset of TX-es

CHIP-2021-02_Group_Tokenization_for_Bitcoin_Cash.md

@@ -7,7 +7,7 @@
         Type: Technical
         Layer: Consensus
         Status: DRAFT
-        Last Edit Date: 2021-04-13
+        Last Edit Date: 2021-04-14
 
 ## Summary
 
@@ -156,11 +156,11 @@ This allows us to:
 - Issue new tokens as long as some MINT UTXO exits.
 - Transfer ownership of the MINT authority the same way ownership of BCH is transferred: by spending it to other addresses.
 - Provably destroy minting capability by spending all MINT carrying UTXOs without creating a MINT authority "change" on the output side.
-- Audit the supply cap i.e. the upper bound of a token supply by scanning the UTXO set, or
-- Audit the token supply cap by walking the sub-DAG of only those transactions which have a MINT on either side.
-This authority subset of a token group is sufficient to prove a supply cap.
-- Produce an SPV proof for that subset to prove the supply cap to light wallets.
-The size of this proof grows linearly with the number of that token group authority transactions, and for many tokens this could be a manageable number of TX-es making these proofs convenient.
+- Audit the token supply fixedness by walking the sub-DAG of only those transactions which have a MINT on either side.
+- The existence of this sub-DAG can be proven to light wallets using an SPV proof, and if there are no lingering MINT UTXOs then the supply is proven fixed.
+- The token amounts from the same TX subset can then be summed to prove the total supply of any fixed-supply token.
+- If a MINT exists, only full nodes will know the current state of a token supply.
+- They could produce an SPV proof, but the verifier has no way of knowing that some UTXOs haven't been spent and the descendand branches witheld from the proof. Such proof only saves the verifier some work, and if he can't tust the node then he still has to verify the proof against the UTXO state.
 
 {TODO: some examples for a full-stack solution, issue [#14](https://gitlab.com/0353F40E/group-tokenization/-/issues/14)}
 
@@ -246,13 +246,6 @@ The actual metadata scheme to be used is beyond the scope of this proposal, and
 
 {TODO: some examples}
 
-#### Metadata Updating
-
-An authority carrying only the BATON, without a MINT or MELT, cannot do anything but pass the lone BATON.
-We don't prohibit this, because it gives users a way to provably signal some operation which doesn't need to be enforced by Group Tokenization consensus, like metadata updating.
-
-{TODO: some examples}
-
 #### Provisions for Future Upgradeability
 
 In order to preserve the possibility of adding future group specific behaviors or contstraints on an opt-in basis, below we describe a final criterion for computing the 32-byte group ID in GENESIS, providing a means to store the token creator's feature selection.  Future features would be applied on a group-basis and would only be available to token groups created after the features had became available, so adding new features would not be able to affect the behavior of previously created token groups.