fix(contracts): OZ-M04 Use of Non-Production-Ready Trusted Forwarder

[zimpha]

Purpose or design rationale of this PR

This PR partially fixed the issue reported by Openzepplin (M-04 Use of Non-Production-Ready Trusted Forwarder). The following are the details:

The GasSwap contract inherits from ERC2771Context thereby allowing meta-transactions to work with its functions. It relies on a trusted forwarder that is set in the constructor. The trusted forwarder that it depends on is the MinimalForwarder , which is located in the External contract. However, the MinimalForwarder is not ready for production use and is mainly meant for testing.

By using the MinimalForwarder , ETH could potentially be lost. In addition, the MinimalForwader's signed requests do not expire and lack batching, which is useful when dealing with a large volume of requests to be forwarded.
Consider using OpenZeppelin's ERC2771Forwarder instead. While this contract is not available until v5.0 is released, the source code can be obtained from the master branch and inserted into the codebase.

PR title

Your PR title must follow conventional commits (as we are doing squash merge for each PR), so it must start with one of the following types:

• fix: A bug fix

Deployment tag versioning

Has tag in common/version.go been updated?

• No, this PR doesn't involve a new deployment, git tag, docker image tag
• Yes

Breaking change label

Does this PR have the breaking-change label?

• No, this PR is not a breaking change
• Yes

[github-actions]

LCOV of commit 2b02052 during Contracts #1388

Summary coverage rate:
  lines......: 51.2% (995 of 1944 lines)
  functions..: 65.2% (223 of 342 functions)
  branches...: no data found

Files changed coverage rate: n/a