Add metadata attribute to REST

[Galadrin]

Proposed changes

Add the possibility to query at a given block in the past
This feature is already avalable with gRPC but need to modify the interface for REST

This patch add the metadata attribute to the REST interface.
Call at height can be made using

metadata = (("x-cosmos-block-height", "123456"),)
bank.Balance(QueryBalanceRequest(address="account", denom="denom"), 
             metadata=metadata)

the metadata can also contain authentication, the metadata ar converted to headers in the REST request

Types of changes

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• Bugfix (non-breaking change that fixes an issue)
• New feature (non-breaking change that adds functionality)
• Breaking change (fix or feature that would cause existing functionality to stop working as expected)
• Something else (e.g. tests, scripts, example, deployment, infrastructure, ...)

Checklist

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• I have read the CONTRIBUTING document.
• I have based my branch, and I am making a pull request against, the main branch.
• Checks and tests pass locally.

If applicable

• I have added tests that prove my fix is effective or that my feature works.
• I have checked that code coverage does not decrease.
• I have added/updated the documentations.

Further comments

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