Add Member proposal custom apply phase

AddMemberProposal.ts

public async applyProposalAsset(store: StateStore): Promise<ApplyProposal> {
 const errors: TransactionError[] = [];
 const proposal = await store.account.getOrDefault(this.getProposalAddress()) as ProposalAccount;
 const addressBook = await store.account.getOrDefault(getAddressFromPublicKey(this.asset.addressBook)) as AddressBookAccount;
 const proposedMember = await store.account.getOrDefault(getAddressFromPublicKey(this.asset.options.member)) as Account;

 if (!this.asset.options.member) {
   errors.push(
     new TransactionError(
       '`.asset.options.member` should contain the proposal.',
       this.id,
       '.asset.options.member',
       undefined,
     ),
   );
 }

 if (addressBook.asset.addresses.find(m => m === this.asset.options.member)) {
   errors.push(
     new TransactionError(
       '`.asset.options.member` already is in this address book.',
       this.id,
       '.asset.options.member',
       this.asset.options.member,
     ),
   );
 }

 if (proposedMember.publicKey === undefined) {
   errors.push(
     new TransactionError(
       '`.asset.options.member` not found on the blockchain.',
       this.id,
       '.asset.options.member',
       this.asset.options.member,
       'not found'
     ),
   );
 }

 proposal.asset = {
   ...proposal.asset,
   type: "ADD_MEMBER",
   options: {
     member: this.asset.options.member ? this.asset.options.member : "",
   },
 }

 return { proposal, errors };
}