chore: add sep45 fields in stellar TOML interface (#1326)

* core: add sep45 fields in stellar TOML interface

SEP-1 TOML files now support `WEB_AUTH_FOR_CONTRACTS_ENDPOINT` and
`WEB_AUTH_CONTRACT_ID` fields for SEP-45 authentication. This
commit adds those two fields to the return type from the
`StellarToml.Resolver.resolve(...)` function.

* use `ContractId` for more consistency with the rest of the SDK

Author: ElliotFriend

src/stellartoml/index.ts

@@ -103,6 +103,7 @@ export namespace Api {
   }
   export type Url = string;
   export type PublicKey = string;
+  export type ContractId = string;
   export type ISODateTime = string;
   export interface Documentation {
     ORG_NAME?: string;
@@ -191,6 +192,8 @@ export namespace Api {
     TRANSFER_SERVER?: Url;
     KYC_SERVER?: Url;
     WEB_AUTH_ENDPOINT?: Url;
+    WEB_AUTH_FOR_CONTRACTS_ENDPOINT?: Url;
+    WEB_AUTH_CONTRACT_ID?: ContractId;
     FEDERATION_SERVER?: Url;
     SIGNING_KEY?: PublicKey;
     HORIZON_URL?: Url;