Postgres: Datasource health check error message improvements #96906 (#96990)

* updated postgres health check error messages

* addressed review comments / added tests

pkg/tsdb/grafana-postgresql-datasource/sqleng/handler_checkhealth_test.go

@@ -0,0 +1,60 @@
+package sqleng
+
+import (
+	"errors"
+	"net"
+	"testing"
+
+	"github.com/grafana/grafana-plugin-sdk-go/backend"
+	"github.com/lib/pq"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestErrToHealthCheckResult(t *testing.T) {
+	tests := []struct {
+		name string
+		err  error
+		want *backend.CheckHealthResult
+	}{
+		{
+			name: "without error",
+			want: &backend.CheckHealthResult{Status: backend.HealthStatusError, Message: "Internal Server Error"},
+		},
+		{
+			name: "network error",
+			err:  errors.Join(errors.New("foo"), &net.OpError{Op: "read", Net: "tcp", Err: errors.New("some op")}),
+			want: &backend.CheckHealthResult{
+				Status:      backend.HealthStatusError,
+				Message:     "Network error: Failed to connect to the server. Error message: some op",
+				JSONDetails: []byte(`{"errorDetailsLink":"https://grafana.com/docs/grafana/latest/datasources/postgres","verboseMessage":"foo\nread tcp: some op"}`),
+			},
+		},
+		{
+			name: "db error",
+			err:  errors.Join(errors.New("foo"), &pq.Error{Message: pq.ErrCouldNotDetectUsername.Error(), Code: pq.ErrorCode("28P01")}),
+			want: &backend.CheckHealthResult{
+				Status:      backend.HealthStatusError,
+				Message:     "foo\npq: pq: Could not detect default username. Please provide one explicitly. Postgres error code: invalid_password",
+				JSONDetails: []byte(`{"errorDetailsLink":"https://grafana.com/docs/grafana/latest/datasources/postgres","verboseMessage":"pq: Could not detect default username. Please provide one explicitly"}`),
+			},
+		},
+		{
+			name: "regular error",
+			err:  errors.New("internal server error"),
+			want: &backend.CheckHealthResult{
+				Status:      backend.HealthStatusError,
+				Message:     "internal server error",
+				JSONDetails: []byte(`{"errorDetailsLink":"https://grafana.com/docs/grafana/latest/datasources/postgres","verboseMessage":"internal server error"}`),
+			},
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			got, err := ErrToHealthCheckResult(tt.err)
+			require.Nil(t, err)
+			assert.Equal(t, string(tt.want.JSONDetails), string(got.JSONDetails))
+			require.Equal(t, tt.want, got)
+		})
+	}
+}