Add device agent library

Provide enrollment, elevated install, posture checks, keystore, and
system-tray helpers shared by the probo-agent binary.

Signed-off-by: Ludovic Vielle <ludovic@probo.com>

pkg/deviceagent/client_test.go

@@ -0,0 +1,77 @@
+// Copyright (c) 2026 Probo Inc <hello@probo.com>.
+//
+// Permission is hereby granted, free of charge, to any person obtaining a copy
+// of this software and associated documentation files (the "Software"), to deal
+// in the Software without restriction, including without limitation the rights
+// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+// copies of the Software, and to permit persons to whom the Software is
+// furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in
+// all copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+// SOFTWARE.
+
+package deviceagent
+
+import (
+	"context"
+	"encoding/json"
+	"net/http"
+	"net/http/httptest"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestClientExchangeEnrollmentToken(t *testing.T) {
+	t.Parallel()
+
+	const wantAPIKey = "device-api-key-secret"
+
+	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		assert.Equal(t, http.MethodPost, r.Method)
+		assert.Equal(t, "/api/agent/v1/enroll", r.URL.Path)
+		assert.Empty(t, r.Header.Get("Authorization"))
+
+		var body struct {
+			Token string `json:"token"`
+		}
+		assert.NoError(t, json.NewDecoder(r.Body).Decode(&body))
+		assert.Equal(t, "enroll-token", body.Token)
+
+		w.Header().Set("Content-Type", "application/json")
+		assert.NoError(t, json.NewEncoder(w).Encode(map[string]string{
+			"api_key": wantAPIKey,
+		}))
+	}))
+	t.Cleanup(srv.Close)
+
+	client := NewClient(srv.URL, "", "probo-agent/test")
+
+	apiKey, err := client.ExchangeEnrollmentToken(context.Background(), "enroll-token")
+	require.NoError(t, err)
+	assert.Equal(t, wantAPIKey, apiKey)
+}
+
+func TestClientExchangeEnrollmentTokenUnauthorized(t *testing.T) {
+	t.Parallel()
+
+	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, _ *http.Request) {
+		http.Error(w, "unauthorized", http.StatusUnauthorized)
+	}))
+	t.Cleanup(srv.Close)
+
+	client := NewClient(srv.URL, "", "probo-agent/test")
+
+	_, err := client.ExchangeEnrollmentToken(context.Background(), "used-token")
+	require.Error(t, err)
+	assert.True(t, IsUnauthorized(err))
+}