Supermarket's `units-for-slot` route integration inside Sentry

[elpiel]

Move Supermarket's GET /units-for-slot to sentry

The market will be fully integrated into the platform and the units-for-slot route will be moved to Sentry.

AdSlot will not be persisted in the database, instead, the whole AdSlot will be used in the adview-manager to generate the ad view code.

Initially for an active status of the Campaign simply use:

• Campaign.active.to > Now
• Is there remaining budget in Campaign (campaign remaining > 0)

Check out the platform issue for more details AmbireTech/adex-platform#625

[elpiel]

Here's a non-exhaustive list of the identified changes required to move and alter the /units-for-slot route to account for the V5 changes:

• HTTP method should be changed to POST
• AdSlot should be POST-ed to the route in order to fetch AdUnits for the particular Ad type
• accepted_referrers, categories & alexa_rank, previously taken from the AdSlotResponse of the Market, should be retrieved from the Platform (see (tracking) AIP#61: AdEx V5: Market integration inside Platform adex-platform#625 for more details)
• Fetch AdSlot.fallback_unit from the Platform (again, see (tracking) AIP#61: AdEx V5: Market integration inside Platform adex-platform#625 for more details)
• depositAsset query parameters can now be renamed to be an array depositAsset[] and even moved to the POST-ed data instead of the query.
• Fetch active Campaigns (should be discussed what this actually means in V5 for this route)

[elpiel]

Supermarket statuses to V5

The statuses of campaigns/channels (in V4) is computed when they are collected from sentry, before they are put into the cache.
Supermarket statuses, in order of the performed checks, linked to their V5 counter parts (if such exist):

❌ - No counterpart in V5
❓ - uncertain if such counterpart exists in V5

1. Is Finalized?
   1.1. Is Channel expired? Utc::now() > channel.valid_until => Is Campaign active Utc::now() > campaign.active.to
   1.2. ❌ Is in withdraw period? Utc::now() > channel.spec.withdraw_period_start
   1.3 Is channel exhausted? total_balances >= channel.deposit_amount => Has remaining budget (in Campaign)?

2. Is (Channel) initializing?

3. Is (Channel) Unsound?
   3.1. Is (Channel) offline?
   3.2. Is (Channel) disconnected?
   3.3. Is rejected state (of Channel)?
   3.4. Is (Channel) healthy?

4. Is (Channel) Active? (This status incorporates both Active & Ready statuses)
   4.1. Is (Channel) Active?
   4.2 Is (Channel) Ready? & channel.spec.active_from < Utc::now() => Is (Channel) Ready? & campaign.active.from < Utc::now()

5. If not Active and all other status checks have passed, then status is Waiting