Add b2_bucket_notification_rules resource and data source

[mlech-reef]

Closes #90

Schema:

resource "b2_bucket_notification_rules" "example" {
  bucket_id = b2_bucket.example.id
  notification_rules {
    name = "test-rule-1"
    event_types = [
      "b2:ObjectCreated:*",
      "b2:ObjectDeleted:*",
    ]
    is_enabled         = true  # optional: default true
    object_name_prefix = ""  # optional, default ""
    target_configuration {  # optional
      target_type                = "webhook"
      url                        = "https://example.com/webhook"
      hmac_sha256_signing_secret = "..." # optional
      custom_headers {  # optional
        name  = "myCustomHeader1"
        value = "myCustomHeaderVal1"
      }
    }
  }
  # is_suspended = false  # computed
  # suspension_reason = ""  # computed
}

data "b2_bucket_notification_rules" "example" {
  bucket_id = b2_bucket.example.bucket_id
  depends_on = [
    b2_bucket_notification_rules.example,
  ]
}

[ppolewicz]

some tests failed

[mlech-reef]

some tests failed

Because the API key doesn't have the proper permissions.