Add new AdTargetingAnalyticsStream stream

[mjn]

What was done?

The Pinterest Ads API supports getting targeting analytics for ads, allowing for reporting on various breakdowns such as country, region, etc. However, the tap-pinterest-ads tap does not currently have a stream to pull this data.

This PR adds a new stream - AdTargetingAnalyticsStream - that fetches data for all currently supported targeting types (AGE_BUCKET_AND_GENDER targeting type has been omitted as it is in beta and not currently available to all users).

The AdTargetingAnalyticsStream is a subclass of AdAnalyticsStream, and leverages the bulk of the parent class code; however, it has a custom post_process method that transforms the record returned by the API so that it more closely resembles the rows produced by the AdAnalyticsStream. For example, the following is an example of a record returned by the API:

{
  "targeting_type": "KEYWORD",
  "targeting_value": "christmas decor ideas",
  "metrics": {
    "AD_GROUP_ID": 2680067996745,
    "DATE": "2022-04-26",
    "SPEND_IN_DOLLAR": 240
  }
}

The post_process function flattens the metrics structure into the root document, so that it looks like the following (Note: All column names have been capitalized to match the naming convention of the current AdAnalyticsStream columns):

{
  "TARGETING_TYPE": "KEYWORD",
  "TARGETING_VALUE": "christmas decor ideas",
  "AD_GROUP_ID": 2680067996745,
  "DATE": "2022-04-26",
  "SPEND_IN_DOLLAR": 240
}

The parent_stream_type property of the AdTargetingAnalyticsStream is set to AdStream as the targeting_analytics API endpoint requires that at least one ad ID be passed as a parameter when querying the API. Thus, once an ad has been extracted in the parent stream, the ad_id is set in the context that is passed to the child stream, allowing the stream to query the targeting analytics for each ad extracted by the AdStream.

[mjn]

The targeting analytics API endpoint does not support querying of reach metrics (even though they are listed in the set of available columns in the API docs, when querying these columns the API returns an error), so I have extracted those columns into a separate array and updated the AdStream to get AD_ANALYTICS_COLUMNS + AD_ANALYTICS_REACH_COLUMNS while AdTargetingAnalyticsStream only gets AD_ANALYTICS_COLUMNS.