[BUG] Operations object should have function channel() instead of channels()

[snailtomatoes]

Describe the bug.

As per spec v3.0.0 Operations are unique and only support a single Channel. Doesn't make much sense to return a Channels object since it should only contain only one Channel.

https://www.asyncapi.com/docs/reference/specification/v3.0.0#operationObject
https://github.com/asyncapi/parser-api/blob/master/docs/api.md

Expected behavior

parser should support operation.channel() and not operation.channels()

Screenshots

How to Reproduce

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👀 Have you checked for similar open issues?

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🏢 Have you read the Contributing Guidelines?

• I have read the Contributing Guidelines

Are you willing to work on this issue ?

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[github-actions]

Welcome to AsyncAPI. Thanks a lot for reporting your first issue. Please check out our contributors guide and the instructions about a basic recommended setup useful for opening a pull request.
Keep in mind there are also other channels you can use to interact with AsyncAPI community. For more details check out this issue.

[smoya]

The Parser-API is not matching 1:1 with any of the spec versions. It is elastic and agnostic enough to adopt any breaking change in the spec without actually causing a breaking change.

That's actually the main mission of this API. You can read more in the README.