Mock services: Implement mock polling and mock issue creation

[anubh-v]

This PR implements the createIssue and pollIssue methods of MockGithubService and MockIssueService respectively.
In these mocked methods, the actual GitHub API is not used, but simply imitated (e.g. createIssue simply returns a new GithubIssue, without using the GitHub API)

With these mocked methods, we can now create new bug reports in our end-to-end tests.

To test these changes: run npm run ng:serve:test.
This starts the app in "test" mode - the app will be using mocked services (hence the GitHub API will not be used).
You should be able to navigate to Bug Reporting Phase and create new bug reports.

Proposed commit message:

Mock services: Implement mock polling and mock issue creation

We cannot create new bug reports in our e2e tests,
as this process relies on the `createIssue` and `pollIssue` methods
of `MockGithubService` and `MockIssueService` respectively,
These methods have not been mocked yet.

Let's write mock implementations of `createIssue` and `pollIssue`,
so that we can create new bug reports in our e2e tests.

[ptvrajsk]

LGTM 👍

[seanlowjk]

Just a question here actually! Do we normally use relative or absolute paths for these kind of common files like package.json o.o

[ptvrajsk]

@seanlowjk

Hmm so far it has been relative links. But we can look into defining an absolute path for package json to make it cleaner but its only used in about 2/3 places I think. Also to define an absolute path we'd need to modify the tsconfig?

[seanlowjk]

Ahhhhh I see.....

Then I think as of now, we can just stick to relative paths :P

[anubh-v]

I've only seen relative paths used in this context. Is there a benefit to using absolute paths?