feat: Add Time configtype

[rhino1998]

Summary

This adds a new Time type to be used in plugin specs that can represent either fixed times or relative times. A future PR should extend the duration parsing to handle days, etc.

kind: source
spec:
  name: "orb"
  registry: "grpc"
  path: "localhost:7777"
  version: "v1.0.0"
  tables:
    ["*"]
  destinations:
    - "sqlite"
  spec:
    api_key: "${CQ_ORB_API_KEY}"
    timeframe_start: 10 days ago
    timeframe_end: "2024-09-25T03:52:40.14157935-04:00"

Here timeframe_start and timeframe_end are both configtype.Time types. Using mixed relative/fixed timestamps for timeframes isn't really useful here as the relative one will be relative to the run-time of the sync but in this example having

timeframe_start: 10 days ago
timeframe_end: now

or even omitting timeframe_end entirely is more useful

timeframe_start: 10 days ago

The plugin is free to define default like so

type Spec struct {
	// TimeframeStart is the beginning of the timeframe in which to fetch cost data.
	TimeframeStart configtype.Time `json:"timeframe_start"`

	// TimeframeEnd is the beginning of the timeframe in which to fetch cost data.
	TimeframeEnd configtype.Time `json:"timeframe_end"`

	// ...
}


func (s *Spec) SetDefaults() {
	if s.TimeframeStart.IsZero() {
		s.TimeframeStart = configtype.NewRelativeTime(-1 * 365 * 24 * time.Hour)
	}

	if s.TimeframeEnd.IsZero() {
		s.TimeframeEnd = configtype.NewRelativeTime(0)
	}
}