Implementation smart contract aggregate

[ghost]

Purpose

To implement Smart Contract features data needs to be fetched and stored as events. These can then later be mapped to endpoints and visualised in the UI.

Design has been written at: https://concordium.atlassian.net/wiki/spaces/EN/pages/1190199324/Design

Task:

• https://concordium.atlassian.net/browse/CBW-1254
• https://concordium.atlassian.net/browse/CBW-1248

Changes

Added a Smart Contract aggregate which can map data either from node or existing data. Existing data are used by a job, which is run prior to the job which continuously fetched data from node.

Checklist

• My code follows the style of this project.
• The code compiles without warnings.
• I have performed a self-review of the changes.
• I have documented my code, in particular the intent of the
  hard-to-understand areas.
• (If necessary) I have updated the CHANGELOG.

[ali-concordium]

We should aim to split the PRs into smaller chunks. In example one PR related to the schema changes only, and a second introducing the aggregate and so forth. Otherwise I can be a bit hard to understand and go through every line, to make sure nothing was missed.

[ali-concordium]

Optional code comments. Feel free to skip whatever you don't agree with.