Referral programme feature updates

[barnabee]

We've received internal stakeholder feedback requesting the following.

Referral programme

• Additional table of tiers mapping number of staked VEGA (staked for at least N epochs, where N is a network parameter) to additional referrer bonus multiple:
  • Referrer receives base share of fees earned by their refereee × staking multiple
  • I believe there will need to be a new net param setting the maximum total portion of fees that can be diverted to a referrer
• Change calculations so that the tier used for calculating the referrers bonus and the referee's discount come from the referee's referral set/team, not the trader's current team.
• [no spec or code change] The staked token requirement to create a referral code should be set to zero at launch. This could be increased later if necessary to mitigate issues.

Other discounts (prev. volume discount)

• In addition to volume discounts for all users
• Add a table of tiers mapping number of staked VEGA (staked for at least N epochs, where N is a network parameter) to additional fee discount rate (%)