fix(http): fix unit tests. Enhance http demo in Starter

[christophercr]

Closes #96

PR Checklist

Please check if your PR fulfills the following requirements:

• The commit message follows our guidelines: https://github.com/NationalBankBelgium/stark/blob/master/CONTRIBUTING.md#-commit-message-guidelines
• Tests for the changes have been added (for bug fixes / features)
• Docs have been added / updated (for bug fixes / features)

PR Type

What kind of change does this PR introduce?

[X] Bugfix
[X] Feature
[ ] Code style update (formatting, local variables)
[ ] Refactoring (no functional changes, no api changes)
[ ] Build related changes
[ ] CI related changes
[ ] Documentation content changes
[ ] Other... Please describe:

What is the current behavior?

• LoggingService and SessionService injections commented since they are not yet implemented
• Only 50% unit tests passing.

Issue Number: #96

What is the new behavior?

• LoggingService and SessionService injections are now used in the service. They are mocked via a factory in the StarkHttp module as a temporary solution until such services are implemented
• 100% unit tests passing

Does this PR introduce a breaking change?

[ ] Yes
[X] No

Other information

Since the LoggingService and the SessionService are not yet implemented, they are mocked and passed to the service via a factory:

const starkHttpServiceFactory = (httpClient: HttpClient) => {
	const logger: any = {
		debug: console.debug,
		warn: console.warn,
		error: console.error,
		correlationId: "dummy-correlation-id"
	};

	const sessionService: any = {
		fakePreAuthenticationHeaders: new Map<string, string>([
			["nbb-dummy-header", "some value"], ["nbb-another-header", "whatever"]
		])
	};

	return new StarkHttpServiceImpl(logger, sessionService, httpClient)
};

@NgModule({
	imports: [
		HttpClientModule
	],
	providers: [
		// FIXME: replace this Factory provider by a simple Class provider once LoggingService and SessionService are implemented
		{provide: starkHttpServiceName, useFactory: starkHttpServiceFactory, deps: [HttpClient]},
	]
})
export class StarkHttpModule {}