[OpenAPI] "format" and "pattern" are different. @format decorator currently only map to "pattern"

[allenjzhang]

OpenAPI "format" contains open value, "pattern" is for regEx. "format":"UUID" ARE widely used in our rest spec.

One choice is to add @pattern and repoint @Format to "format". Thoughts?

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https://swagger.io/docs/specification/data-models/data-types/

[markcowl]

format: bytes
format: dateTime
format: uuid

• move format decorator -> pattern
• add a format decorator whose value is transmitted directly to openAPI
• @format("uuid") foo: string results in swagger with type: string, format: uuid, results in generators
• we have built-in types for datetime, bytes, binary