Implement multisignature pooling service

[MichalTuleja]

Description

According to proposals to the network consensus, enable behalf of user interfaces to create multisignature groups, initiate transactions and sign pending multisignature transactions, store with an incomplete/complete set off signatures, retrieve pending multisig accounts & transaction, mark rejected transactions and remove transaction once it is confirmed or expired

Task

• Implement multisignature transaction broadcast validation #174
• Implement multisignature transaction broadcasting #175
• Multisignature pool quality assurance #177

Sprint 36

• Create microservice for multisignature pool #159
• Create database for transaction pooling #164

Sprint 37

• Create multisignature transaction action #160

Sprint 40

• Retrieve multisignature transaction by ID (GET) #165
• Retrieve multisignature transaction by account (GET) #166

Sprint 41

• Multisignature support for other transaction types #173
• Implement multisignature transaction validation schemes #170
• Create deterministic ID generator #762
• Add signature to multisignature transaction #161
• Create API endpoint for multisignature transaction initiation (POST) #162
• Create API endpoint for multisignature transaction update (PATCH) #163
• Create API endpoint for transaction rejection (DELETE) #168
• Request multisignature transaction rejection #167
• Implement multisignature pool cleanup #176
• Delegate status must be renamed to ineligible #843
• Add multisignature account registration (POST) #172
• Implement multisignature transaction validators #169