add unit tests + mock service

index.ts

package-lock.json

package.json

src/getRole.ts

src/services/association.service.ts

src/services/balance.service.ts

src/services/createToken.ts

src/services/proposal.service.ts

src/services/token.service.ts

src/types/Association.ts

src/types/Proposal.ts

src/types/Role.ts

test/services/balance.service.spec.ts

test/services/token.service.spec.ts