feat: Incur fixed cost for each x/ssi message

[arnabghose997]

Description

This PR aims to make x/ssi message incur fixed fees. Fees for each message is distinct and parameterised under x/ssi module. The rationale behind this has been described in HIP-9.

Implementation

Rules

• If a transaction contains one SSI message (e.g. MsgCreateDID), then it will incur the exact cost as the current CreateDID fee. This is irrespective of the size of the message
• If there are 2 or more SSI messages, the required fees would be the total sum of all fixed-fee cost of each SSI message. For example, lets say MsgCreateDID costs 4000uhid and MsgCreateSchema costs 2000uhid, the required fees would be 6000uhid
• It should be noted that the user provided fees MUST MATCH with the required fees. For instance, if the required fees for a SSI transaction is 7500uhid, the user must provide 7500uhid as fee. Any value above or below 7500uhid is treated as invalid.
• Since, SSI messages incur fixed cost and thus independent of gas consumption, they are NOT allowed to be grouped together with transaction messages of other SDK modules.

Ante Handlers

The x/ssi ante handlers SSITxDecorator, MempoolFeeDecorator and DeductFeeDecorator come together to perform the necessary verification to filter fixed-fee SSI messages and nominal non-SSI messages, and meter fixed charge for SSI messages. Order of calling ante handlers is crucial, and hence the position of these handlers should not be changed, unless a logic change is needed.

Governance Proposal

Any change of fee parameters of SSI transactions can be done by submitting a Param Change Governance Proposal. This type of Governance Proposal requires a JSON file (if done through CLI), describing the new values for consensus parameter(s), to be provided. Following is the format for changing the fixed-fee value of MsgCreateDID to 4578uhid

{
  "title": "Change CreateDID Fee to 4578uhid",
  "description": "Change CreateDID Fee to 4578uhid",
  "changes": [
    {
      "subspace": "ssi",
      "key": "CreateDidFee",
      "value": {"denom": "uhid","amount": "4578"}
    }
  ],
  "deposit": "10000000uhid"
}

Querying current fixed fee

Querying the current fixed-fee for SSI transactions can be done through following methods:

1. CLI

$ hid-noded q ssi list-fees

create_did_fee:
  amount: "4000"
  denom: uhid
create_schema_fee:
  amount: "2000"
  denom: uhid
deactivate_did_fee:
  amount: "1000"
  denom: uhid
register_credential_status_fee:
  amount: "2000"
  denom: uhid
update_did_fee:
  amount: "1000"
  denom: uhid

2. API

GET: <API_HOST>/hypersign-protocol/hidnode/ssi/fixedfee

{
  "create_did_fee": {
    "denom": "uhid",
    "amount": "4000"
  },
  "update_did_fee": {
    "denom": "uhid",
    "amount": "1000"
  },
  "deactivate_did_fee": {
    "denom": "uhid",
    "amount": "1000"
  },
  "create_schema_fee": {
    "denom": "uhid",
    "amount": "2000"
  },
  "register_credential_status_fee": {
    "denom": "uhid",
    "amount": "2000"
  }
}