Header information migration

[pmespresso]

• https://api-01.polkascan.io/kusama/api/v1/eras/
• https://api-01.polkascan.io/kusama/api/v1/block/{blockNumber}
• https://api-01.polkascan.io/kusama/api/v1/session/session/{sessionNumber}

[nyetwurk]

None of those endpoints work.