Update transition to Approve considering the expense classes

Purpose:
Requirement from the UX ticket: Each expense class has a code/number (extention) that compliments the external account number of any fund it is assigned to

Requirements/Scope:

1. Update creation of voucher lines upon invoice approval

Approach:

• If expenseClassId specified in fundDistribution:
  • retrieve expense classes by id
  • add extension number to external account number (externalAccountNumber-extensionNumber)
• group fundDistribution by externalAccountNumber (consider same externalAccountNumbers with different extension numbers as separate external account numbers)
• create voucher line for each externalAccountNumber or externalAccountNumber-extensionNumber and this pair must be store in voucher line field "ExternalAccountNumber"

Acceptance criteria:

• logic updated
• unit tests updated
• API tests updated