Provider need to be updated to new API v2 version

[naxim92]

╷
│ Error: Error creating Alertmanager config
│
│ with mimirtool_alertmanager.demo,
│ on alertmanager.tf line 15, in resource "mimirtool_alertmanager" "demo":
│ 15: resource "mimirtool_alertmanager" "demo" {
│
│ Failed to create Alertmanager config via POST: POST request to
│ http://mimir.example.com/alertmanager/api/v1/alerts failed: server
│ returned HTTP status: 410 Gone, body:
│ "{"status":"deprecated","error":"The Alertmanager v1 API was
│ deprecated in version 0.16.0 and is removed as of version 0.28.0 - please
│ use the equivalent route in the v2 API"}\n"

[wilfriedroset]

Hello @naxim92 would you be able to elaborate more about your issue so that we can reproduce and fix or submit a patch?

I've updated the CI to test against multiple Mimir version and everything pass. This means we have a gap in our test suite.