[misc] Move shared components to shared directory (#4286)

Moved the following directories:

```
  - management/client → shared/management/client
  - management/domain → shared/management/domain
  - management/proto → shared/management/proto
  - signal/client → shared/signal/client
  - signal/proto → shared/signal/proto
  - relay/client → shared/relay/client
  - relay/auth → shared/relay/auth
```

and adjusted import paths

shared/management/client/rest/impersonation.go

@@ -0,0 +1,48 @@
+package rest
+
+import (
+	"net/http"
+	"net/url"
+)
+
+// Impersonate returns a Client impersonated for a specific account
+func (c *Client) Impersonate(account string) *Client {
+	client := NewWithOptions(
+		WithManagementURL(c.managementURL),
+		WithAuthHeader(c.authHeader),
+		WithHttpClient(newImpersonatedHttpClient(c, account)),
+	)
+	return client
+}
+
+type impersonatedHttpClient struct {
+	baseClient HttpClient
+	account    string
+}
+
+func newImpersonatedHttpClient(c *Client, account string) *impersonatedHttpClient {
+	if hc, ok := c.httpClient.(*impersonatedHttpClient); ok {
+		hc.account = account
+		return hc
+	}
+
+	return &impersonatedHttpClient{
+		baseClient: c.httpClient,
+		account:    account,
+	}
+}
+
+func (c *impersonatedHttpClient) Do(req *http.Request) (*http.Response, error) {
+	parsedURL, err := url.Parse(req.URL.String())
+	if err != nil {
+		return nil, err
+	}
+
+	query := parsedURL.Query()
+	query.Set("account", c.account)
+	parsedURL.RawQuery = query.Encode()
+
+	req.URL = parsedURL
+
+	return c.baseClient.Do(req)
+}