Min ticket size should be set based on ETO phase not globally

[Vanilizer]

Currently issuer can set one min. ticket size and max. ticket size for the whole ETO.

However the ETO can have three different phases:

• privale presale (off-chain, option agreements, "fixed slots")
• public presale (on-chain, whitelist)
• public sale

Setting up those phases is part of the fundraising strategy and tehrefore the min. ticket size should be also part of this strategy. Issuer will want to set different min. ticket sizes for different phases, same as discount.

Please add min. ticket size settings to each phase, max. ticket size can just stay "undefined" meaning max. 5M EUR.