[CAD-2449] Add API endpoint for checking valid pool id.

[ksaric]

https://jira.iohk.io/browse/CAD-2449

This works correctly but requires the full resync from the blockchain since we need to add pool ids from the beginning of the blockchain.
This can be achieved using the added command which removes all blockchain-related state and forces a resync:

SMASHPGPASSFILE=config/pgpass stack run smash-exe -- force-resync --mdir ./schema --config config/shelley-qa-config.yaml

Example of how it works.
The existing pool id:

curl -X GET http://localhost:3100/api/v1/exists/8517fa7042cb9494818861c53c87780b4975c0bd402e3ed85168aa66 
{"poolId":"8517fa7042cb9494818861c53c87780b4975c0bd402e3ed85168aa66"}

Non-existing pool id:

curl -X GET http://localhost:3100/api/v1/exists/8517fa7042cb9494818861c53c87780b4975c0bd402e3ed85168aa65
{"code":"RecordDoesNotExist","description":"The requested record does not exist."}

[ksaric]

#82

Will notify once we create a release.

[ksaric]

bors try

[iohk-bors]

try

Build failed:

• ci/hydra-build:required

[ksaric]

bors try

[iohk-bors]

try

Build failed:

• ci/hydra-build:required