Improve test suite by adding integration tests with Grafana

[amotl]

Hi there,

currently, grafana-client employs testing solely by mocking HTTP conversations. Because this does not cover real integration tests with Grafana, it is easy to miss regressions, like those which recently happened here.

• Fix handling 204 No Content responses from Grafana HTTP API #44
• Regression with delete_folder in Grafana 9.3.0 #47
• HTTP API: Regression on 9.3.0 and 8.5.16 with DELETE /api/folders/{UID} grafana/grafana#59546

On the other hand, both grafana-wtf, and Kotori, already feature such an integration test suite with Grafana. In this manner, the grafana-wtf test harness was able to catch this issue.

• CI: Update to Grafana 8.5.21 and 9.4.3 grafana-wtf#44

So, grafana-client will need to adopt that test suite soon, in order to improve compatibility and QA on different versions of Grafana, by adding them to a test matrix.

grafana-wtf/tests can be an inspiration for this. While being at it, we may split this off into a generic pytest-grafana package, in the same spirit like the recently conceived pytest-mqtt package.

With kind regards,
Andreas.

[amotl]

See also suggestion by @lilatomic.

• Feature: specify grafana organisation for client #127 (comment)