Add Canton EA to read from Canton participant node

[cl-mayowa]

Closes #DS-1113

https://smartcontract-it.atlassian.net/browse/DS-1113

Description

This is a general-purpose Chainlink External Adapter that enables smart contracts to read data from Canton participant nodes via the Ledger API. The adapter should be pluggable and configurable to support application-specific queries while maintaining a standard interface.

We should prioritise using the JSON Ledger API interface, although there is an alternative gRPC interface. The ledger API is the interface to the participant node.

This can be used in a more specific way to read from individual DPs, who may have contracts with different getter functions.
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Changes

• High level
• changes that
• you made

Steps to Test

1. Steps
2. to
3. test

Quality Assurance

• If a new adapter was made, or an existing one was modified so that its environment variables have changed, update the relevant infra-k8s configuration file.
• If a new adapter was made, or an existing one was modified so that its environment variables have changed, update the relevant adapter-secrets configuration file or update the soak testing blacklist.
• If a new adapter was made, or a new endpoint was added, update the test-payload.json file with relevant requests.
• The branch naming follows git flow (feature/x, chore/x, release/x, hotfix/x, fix/x) or is created from Jira.
• This is related to a maximum of one Jira story or GitHub issue.
• Types are safe (avoid TypeScript/TSLint features like any and disable, instead use more specific types).
• All code changes have 100% unit and integration test coverage. If testing is not applicable or too difficult to justify doing, the reasoning should be documented explicitly in the PR.

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🦋 Changeset detected

Latest commit: acb7400

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
@chainlink/canton-functions-adapter	Major

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[mmcallister-cll]

not sure what these new toplevel files are, maybe add them to the gitignore file.

[mmcallister-cll]

0.0.0

[mmcallister-cll]

Is this/are these env vars unique to each contract or to the chain itself?

Reason i'm asking is if we intend to reuse this EA for multiple separate contract calls, you'd either want these to be variable & prefixed with a selector name or set in the request params rather than a single env var here.

[mmcallister-cll]

can remove this line

[mmcallister-cll]

is this true for every contract?