Return date-time in OpenApi/autorest-compatible format

[davidyuk]

Currently, dates have been returned in milliseconds since 1970, encoded as integers:

          "time": {
            "description": "The time",
            "type": "integer"
          },

The closest date format supported by autorest is:

          "time": {
            "description": "The time",
            "type": "integer",
            "format": "unixtime"
          },

But the value is expected to be a number of seconds. And it can't be a fraction as I see.

The format which supports milliseconds is RFC3339, e.g. "2024-08-14T12:21:37.468Z":

          "time": {
            "description": "The time",
            "type": "string",
            "format": "date-time"
          },

An advantage of this format is that it is human-readable.

So, to improve the developer experience, I propose returning all times in one of the above formats. The way it is currently implemented in the middleware is the same as in the node, but I'm going to propose the same thing to the node.

https://swagger.io/docs/specification/data-models/data-types/#string
http://azure.github.io/autorest/openapi/formats.html

[davidyuk]

Field names that are good to convert to dates:

• time
• micro_time
• approximate_activation_time
• approximate_expire_time
• register_time
• block_time
• activation_time
• creation_time
• microtime
• last_updated_time

Also, start_date and end_date in stats.

[vatanasov]

I think it is best we keep it the same as the node. If a consensus is reached on the node issue, that leads to a change, we can then also make the change.