Reconsider feeType enum

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Currently the Profile.ModeratorInfo.Fee.FeeType value is ambiguous and we should consider improving or removing the field entirely.

Argument in favor of removal:

• feeType has the following enums: FIXED, PERCENTAGE, and FIXED_WITH_PERCENTAGE where both FIXED and PERCENTAGE can be represented by just FIXED_PLUS_PERCENTAGE values (because we allow 0 values for either/both fixedFee.Amount or/and percentage amounts)
• The only value this field appears to have is for validation which it cannot do since the fields allows both/either of the above fields to also be empty/zero (which go does not differentiate between).

Argument in favor of improvement:

• If the field is meant for validation, we should introduce NO_FEE and protect the feeType inputs as follows:
• • NO_FEE requires 0 for both fixedFee and percentage
• • FIXED_FEE requires 0 for percentage and postivie value for fixedFee.Amount
• • PERCENTAGE requires 0 for fixedFee.Amount and postivie value for percentage
• • FIXED_PLUS_PERCENTAGE requires postivie value for percentage and fixedFee.Amount

This can be discussed and included on the next schema change proposal.