Baseline, assets join table and soft-delete

[pedrolucasp]

This combines with #57 and the data migration script has been run.

Manual data migration is needed;

INSERT INTO assets_nfts (asset_id, nft_id, asset_type, assigned_by, assigned_at, active)
(
SELECT "A", "B", assets.asset_type, owner_id, assets.created_at, true  FROM "_AssetToNFT"
    INNER JOIN assets ON "_AssetToNFT"."A" = assets.id
    inner join contracts c on assets.contract_id = c.id
    inner join wallets w on c.owner_id = w.id 
)
;

[tbergmueller]

• Updated manual migration in first comment of the merge request
• Tested extensively and manually (also already test-deployed to production yiiiiek)