Improve our tests

For the repo of messaging api, I think we should isolate tests by cleaning up data frequently, the tests are getting complicated in files https://github.com/Greenstand/treetracker-messaging-api/blob/main/api-tests/message-api.spec.js it's easy that those data created by tests interfere with each other. And tests shouldn't rely on each other, I found in another project, that the test platform can not promise all these tests to get executed in sequence. Use API like: beforeEach we can clean and isolate all tests.