Build Itemized contributions Backend

[rwalek668]

@alessandro-pianetta is leading the frontend changes for this FR which essentially involves enabling users to see each individual contribution made to committees. To enable this, we need the backend to return the requisite data. Alex proposed a potential backend API (which has not yet been solidified):
[{
ID,
committeeName,
totalContributions,
contributors: [{
name,
contributorType,
occupation,
employer
zipCode,
contributionAmount,
contributionDate
}]
}]