TUN-8735: add managed/local log collection

## Summary
Adds a log collector for the managed/local runtimes.


Closes TUN-8735 TUN-8736

diagnostic/client.go

@@ -0,0 +1,101 @@
+package diagnostic
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+	"net/http"
+	"net/url"
+	"strconv"
+
+	"github.com/cloudflare/cloudflared/logger"
+)
+
+const configurationEndpoint = "diag/configuration"
+
+type httpClient struct {
+	http.Client
+	baseURL url.URL
+}
+
+func NewHTTPClient(baseURL url.URL) *httpClient {
+	httpTransport := http.Transport{
+		TLSHandshakeTimeout:   defaultTimeout,
+		ResponseHeaderTimeout: defaultTimeout,
+	}
+
+	return &httpClient{
+		http.Client{
+			Transport: &httpTransport,
+			Timeout:   defaultTimeout,
+		},
+		baseURL,
+	}
+}
+
+func (client *httpClient) GET(ctx context.Context, url string) (*http.Response, error) {
+	req, err := http.NewRequestWithContext(ctx, http.MethodGet, url, nil)
+	if err != nil {
+		return nil, fmt.Errorf("error creating GET request: %w", err)
+	}
+
+	req.Header.Add("Accept", "application/json;version=1")
+
+	response, err := client.Do(req)
+	if err != nil {
+		return nil, fmt.Errorf("error GET request: %w", err)
+	}
+
+	return response, nil
+}
+
+type LogConfiguration struct {
+	logFile      string
+	logDirectory string
+	uid          int // the uid of the user that started cloudflared
+}
+
+func (client *httpClient) GetLogConfiguration(ctx context.Context) (*LogConfiguration, error) {
+	endpoint, err := url.JoinPath(client.baseURL.String(), configurationEndpoint)
+	if err != nil {
+		return nil, fmt.Errorf("error parsing URL: %w", err)
+	}
+
+	response, err := client.GET(ctx, endpoint)
+	if err != nil {
+		return nil, err
+	}
+
+	defer response.Body.Close()
+
+	var data map[string]string
+	if err := json.NewDecoder(response.Body).Decode(&data); err != nil {
+		return nil, fmt.Errorf("failed to decode body: %w", err)
+	}
+
+	uidStr, exists := data[configurationKeyUID]
+	if !exists {
+		return nil, ErrKeyNotFound
+	}
+
+	uid, err := strconv.Atoi(uidStr)
+	if err != nil {
+		return nil, fmt.Errorf("error convertin pid to int: %w", err)
+	}
+
+	logFile, exists := data[logger.LogFileFlag]
+	if exists {
+		return &LogConfiguration{logFile, "", uid}, nil
+	}
+
+	logDirectory, exists := data[logger.LogDirectoryFlag]
+	if exists {
+		return &LogConfiguration{"", logDirectory, uid}, nil
+	}
+
+	return nil, ErrKeyNotFound
+}
+
+type HTTPClient interface {
+	GetLogConfiguration(ctx context.Context) (LogConfiguration, error)
+}