Plugin E2E: Interact with Grafana http api on behalf of logged in user

[sunker]

What this PR does / why we need it:

If a plugin has implemented RBAC, it may be necessary to run different tests suites for different user roles. Plugin-e2e offers a declarative way to create new users with a role in a setup project. In the following example, a new users with Viewer role is created in the setup project, and all tests in the run-tests-for-viewer project starts already authenticated as that user.

//playwright.config.ts
projects: [
      {
        name: 'createViewerUserAndAuthenticate',
        testDir: pluginE2eAuth,
        testMatch: [/.*auth\.setup\.ts/],
        use: {
          user: {
            user: 'viewer',
            password: 'password',
            role: 'Viewer',
          },
        },
      },
      {
        name: 'run-tests-for-viewer',
        testDir: './tests/viewer',
        use: {
          ...devices['Desktop Chrome'],
          // @grafana/plugin-e2e writes the auth state to this file,
          // the path should not be modified
          storageState: 'playwright/.auth/viewer.json',
        },
        dependencies: ['createViewerUserAndAuthenticate'],
      },
  ]

It's important to keep in mind that two different users (or credentials) are in play here. First, it's the credentials used to call the Grafana Http API to create the new user. These credentials requires elevated permissions. Secondly, it's the user being used to run the tests, which in this case has restricted permissions (viewer role).

Until now, the admin user used to interact with the Grafana http api has been using basic auth. This is not ideal since basic auth is disabled for scaffolded plugins. This PR changes that so that any interaction with the Grafana http api is done on behalf of a logged in user. Additionally, I've refactored the code so that all interactions with the Grafana api is encapsulated in a GrafanaAPIClient file. This helps separating the two concepts.

Which issue(s) this PR fixes:

Fixes ##968

Special notes for your reviewer:

📦 Published PR as canary version: Canary Versions

✨ Test out this PR locally via:

npm install @grafana/[email protected]
npm install @grafana/[email protected]
# or 
yarn add @grafana/[email protected]
yarn add @grafana/[email protected]

[github-actions]

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[Ukochka]

LGTM!

[grafana-plugins-platform-bot]

🚀 PR was released in @grafana/[email protected], @grafana/[email protected] 🚀