Specify that Datetime values should be ISO strings

[lorensr]

Fixes #154

(I think Datetime representation is the only ambiguity—the rest isn't needed, since precise field type info is only needed in AddSearchAttributesRequest)

[cretz]

I think there is even more clarity than this needed. ISO8601 has multiple string formats (not to be confused w/ RFC3389 and other additions many things make to those). Can you specify exact format here? If unsure, we can start with where they are converted to date (Go? ES?) and then get the exact format from there.

[lorensr]

I think Go does

var val time.Time
json.Unmarshal(payload.GetData(), &val)

and json.Unmarshal calls this?

https://pkg.go.dev/time#Time.UnmarshalJSON

which uses an RFC 3339 string. I'll edit to say that.

Other research, for posterity:

On ES side, Server has a v7 client and v6 client. v7 is date_nanos, and v6 is date:

v6:

		case enumspb.INDEXED_VALUE_TYPE_DATETIME:
			typeMap = map[string]interface{}{"type": "date"}
		}

Neither appears to customize format, so

• default date_nanos format: "strict_date_optional_time_nanos||epoch_millis"

• default date format: "strict_date_optional_time||epoch_millis"

What's working for me in tctl and web UI:

tctl workflow list --query 'StartTime < "2022-03-04T16:11:33.388Z"'
tctl workflow list --query 'StartTime < "2022-03-04T16:11:33.388000Z"'
tctl workflow list --query 'StartTime < "1646410293388"'

Doesn't work:

tctl workflow list --query 'StartTime < 1646410293388'

Works for me in TS SDK (starting workflow with custom searchAttributes):

"2022-03-04T16:11:33.388Z"
"2022-03-04T16:11:33.388000Z"

Doesn't work:

1646410293388 // gRPC error '1.646410293388e+12 is not a valid value for search attribute CustomDatetimeField of type Datetime',
"1646410293388" // gRPC Error '1646410293388 is not a valid value for search attribute CustomDatetimeField of type Datetime',

[cretz]

Does 2001-02-03T04:05:06+0000 which is a perfectly valid ISO-8601 string work?

It does not in Go using RFC3339 format. If this does not work, we need to document that this is not exactly ISO-8601. Notice https://docs.temporal.io/visibility states:

a string in RFC3339Nano format (such as "2006-01-02T15:04:05.999999999Z07:00").

Need to clarify the same in docs here if it applies.