Rather than replying with null, which complicates using the returned promise
efficiently, we'll respond with a unique error that allows us to distinguish
between a database failure and a missing token.
These are more traditional errors, but we're moving toward structured
logging, so I want error objects that provide more context. I'll explore
that a bit more in next commit. Unfortunately, the untypedness of Promise
rejections make for a less than desirable situation here. Async/await is
not yet an option since we're still compiling to ES5 (have to support
IE11), and TS compiles async/await into generators for environments that
don't support them, which also are not available in ES5.
* src/server/service/TokenedService.js (_getQuoteToken): Remove null check,
since this situation can no longer occur.
* src/server/token/MongoTokenDao.ts (getToken): Remove null from return type
union; reject with `UnknownTokenError' instead.
* src/server/token/TokenDao.ts: Modify interface accordingly.
* src/server/token/UnknownTokenError.ts: New class.
* test/server/token/MongoTokenDaoTest.ts: Modify tests accordingly. Add
missing test for latest token namespace missing.