Introduce query timeout configuration (#2157)

## Summary

Implements configurable query execution timeout controls to prevent
poorly optimized or excessive queries from consuming excessive server
resources, causing performance degradation, or crashing the Zabbix
server.

Fixes: https://github.com/grafana/oss-big-tent-squad/issues/127

## Problem

Previously, the plugin only had an HTTP connection timeout (`timeout`)
that controlled individual API request timeouts. However, a complete
query execution could involve multiple API calls and run indefinitely if
not properly controlled, potentially causing resource exhaustion.

## Solution

Added a new `queryTimeout` setting that enforces a maximum execution
time for entire database queries initiated by the plugin. Queries
exceeding this limit are automatically terminated with proper error
handling and logging.

## Testing

1. Configure a datasource with `queryTimeout` set to a low value (e.g.,
5 seconds)
2. Execute a query that would normally take longer than the timeout
3. Verify that:
   - Query is terminated after the timeout period
   - Error message indicates timeout occurred
   - Logs contain timeout warning with query details
   - Other queries in the same request continue to execute

## Notes

- `queryTimeout` is separate from `timeout` (HTTP connection timeout)
- `queryTimeout` applies to the entire query execution, which may
involve multiple API calls
- Default value of 60 seconds ensures reasonable protection while
allowing normal queries to complete
- Timeout errors are logged with query refId, queryType, timeout
duration, and datasourceId for troubleshooting

pkg/datasource/datasource_test.go

@@ -2,8 +2,12 @@ package datasource
 
 import (
 	"context"
+	"encoding/json"
+	"strings"
 	"testing"
+	"time"
 
+	"github.com/alexanderzobnin/grafana-zabbix/pkg/settings"
 	"github.com/grafana/grafana-plugin-sdk-go/backend"
 	"gotest.tools/assert"
 )
@@ -66,3 +70,101 @@ func TestZabbixBackend_getCachedDatasource(t *testing.T) {
 		})
 	}
 }
+
+func TestQueryData_QueryTimeoutConfiguration(t *testing.T) {
+	tests := []struct {
+		name            string
+		queryTimeout    interface{}
+		expectedTimeout time.Duration
+		description     string
+	}{
+		{
+			name:            "Default timeout when not configured",
+			queryTimeout:    nil,
+			expectedTimeout: 60 * time.Second,
+			description:     "Should use default 60 seconds when queryTimeout is not set",
+		},
+		{
+			name:            "Default timeout when zero",
+			queryTimeout:    0,
+			expectedTimeout: 60 * time.Second,
+			description:     "Should use default 60 seconds when queryTimeout is 0",
+		},
+		{
+			name:            "Custom timeout configured",
+			queryTimeout:    30,
+			expectedTimeout: 30 * time.Second,
+			description:     "Should use configured queryTimeout value",
+		},
+		{
+			name:            "Custom timeout as string",
+			queryTimeout:    "45",
+			expectedTimeout: 45 * time.Second,
+			description:     "Should parse string queryTimeout value",
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			// Create datasource settings with queryTimeout
+			jsonData := map[string]interface{}{
+				"queryTimeout": tt.queryTimeout,
+			}
+			jsonBytes, _ := json.Marshal(jsonData)
+
+			dsSettings := backend.DataSourceInstanceSettings{
+				ID:       1,
+				Name:     "TestDatasource",
+				URL:      "http://zabbix.org/zabbix",
+				JSONData: jsonBytes,
+			}
+
+			// Parse settings to verify timeout is set correctly
+			zabbixSettings, err := settings.ReadZabbixSettings(&dsSettings)
+			assert.NilError(t, err)
+			assert.Equal(t, tt.expectedTimeout, zabbixSettings.QueryTimeout, tt.description)
+		})
+	}
+}
+
+func TestQueryData_QueryTimeoutContextCreation(t *testing.T) {
+	// Test that query timeout context is properly created with the configured timeout
+	jsonData := map[string]interface{}{
+		"queryTimeout": 5, // 5 seconds
+	}
+	jsonBytes, _ := json.Marshal(jsonData)
+
+	dsSettings := backend.DataSourceInstanceSettings{
+		ID:       1,
+		Name:     "TestDatasource",
+		URL:      "http://zabbix.org/zabbix",
+		JSONData: jsonBytes,
+	}
+
+	// Verify queryTimeout is set correctly
+	zabbixSettings, err := settings.ReadZabbixSettings(&dsSettings)
+	assert.NilError(t, err)
+	assert.Equal(t, 5*time.Second, zabbixSettings.QueryTimeout)
+
+	// Test that context with timeout is created correctly
+	ctx := context.Background()
+	queryCtx, cancel := context.WithTimeout(ctx, zabbixSettings.QueryTimeout)
+	defer cancel()
+
+	// Verify context has deadline set
+	deadline, ok := queryCtx.Deadline()
+	assert.Assert(t, ok, "Context should have a deadline")
+	assert.Assert(t, deadline.After(time.Now()), "Deadline should be in the future")
+	assert.Assert(t, deadline.Before(time.Now().Add(6*time.Second)), "Deadline should be approximately 5 seconds from now")
+}
+
+func TestQueryData_QueryTimeoutErrorMessage(t *testing.T) {
+	// Test that timeout error message contains the expected information
+	timeoutMsg := "Query execution exceeded maximum allowed time (5s). Query was automatically terminated to prevent excessive resource consumption."
+
+	// Verify error message format
+	assert.Assert(t, strings.Contains(timeoutMsg, "Query execution exceeded maximum allowed time"))
+	assert.Assert(t, strings.Contains(timeoutMsg, "5s"))
+	assert.Assert(t, strings.Contains(timeoutMsg, "automatically terminated"))
+	assert.Assert(t, strings.Contains(timeoutMsg, "prevent excessive resource consumption"))
+}