Backend plugins: Implement support for resources (#21805)

Implements initial support for resources using v0.14.0 of SDK.

Ref #21512

pkg/plugins/backendplugin/contracts.go

@@ -0,0 +1,85 @@
+package backendplugin
+
+import (
+	"encoding/json"
+	"strconv"
+
+	"github.com/grafana/grafana-plugin-sdk-go/genproto/pluginv2"
+)
+
+// HealthStatus is the status of the plugin.
+type HealthStatus int
+
+const (
+	// HealthStatusUnknown means the status of the plugin is unknown.
+	HealthStatusUnknown HealthStatus = iota
+	// HealthStatusOk means the status of the plugin is good.
+	HealthStatusOk
+	// HealthStatusError means the plugin is in an error state.
+	HealthStatusError
+)
+
+var healthStatusNames = map[int]string{
+	0: "UNKNOWN",
+	1: "OK",
+	2: "ERROR",
+}
+
+func (hs HealthStatus) String() string {
+	s, exists := healthStatusNames[int(hs)]
+	if exists {
+		return s
+	}
+	return strconv.Itoa(int(hs))
+}
+
+// CheckHealthResult check health result.
+type CheckHealthResult struct {
+	Status HealthStatus
+	Info   string
+}
+
+func checkHealthResultFromProto(protoResp *pluginv2.CheckHealth_Response) *CheckHealthResult {
+	status := HealthStatusUnknown
+	switch protoResp.Status {
+	case pluginv2.CheckHealth_Response_ERROR:
+		status = HealthStatusError
+	case pluginv2.CheckHealth_Response_OK:
+		status = HealthStatusOk
+	}
+
+	return &CheckHealthResult{
+		Status: status,
+		Info:   protoResp.Info,
+	}
+}
+
+type PluginInstance struct {
+	ID       int64
+	Name     string
+	Type     string
+	URL      string
+	JSONData json.RawMessage
+}
+
+type PluginConfig struct {
+	PluginID string
+	OrgID    int64
+	Instance *PluginInstance
+}
+
+type CallResourceRequest struct {
+	Config  PluginConfig
+	Path    string
+	Method  string
+	URL     string
+	Headers map[string][]string
+	Body    []byte
+}
+
+// CallResourceResult call resource result.
+type CallResourceResult struct {
+	Status  int
+	Headers map[string][]string
+	Body    []byte
+}