feat: initial release with 48 Mattermost MCP tools

- 27 base tools: channels, messaging, users, reactions, files, DMs
- Team management: invite/remove users, get stats, list members
- Slash commands: execute /remind, /poll, etc.
- Webhook management: incoming and outgoing webhooks
- System tools: server config, logs, bulk status updates
- Channel admin: create, invite, leave, delete channels
- Read-only mode for safe exploration
- Dual token support (bot + PAT) for enhanced security
- Apache 2.0 licensed

pkg/mattermost/client_test.go

@@ -0,0 +1,39 @@
+package mattermost
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestNewClient(t *testing.T) {
+	client := NewClient("https://test.mattermost.com", "bot-token", "pat-token")
+	assert.NotNil(t, client)
+	assert.Equal(t, "https://test.mattermost.com", client.host)
+	assert.Equal(t, "bot-token", client.botToken)
+	assert.Equal(t, "pat-token", client.pat)
+}
+
+func TestGetToken_ReadOperation(t *testing.T) {
+	client := NewClient("https://test.mattermost.com", "bot-token", "pat-token")
+	token := client.getToken(false)
+	assert.Equal(t, "bot-token", token)
+}
+
+func TestGetToken_WriteOperation(t *testing.T) {
+	client := NewClient("https://test.mattermost.com", "bot-token", "pat-token")
+	token := client.getToken(true)
+	assert.Equal(t, "pat-token", token)
+}
+
+func TestGetToken_FallbackToPAT(t *testing.T) {
+	client := NewClient("https://test.mattermost.com", "", "pat-token")
+	token := client.getToken(false)
+	assert.Equal(t, "pat-token", token)
+}
+
+func TestSetGlobalClient(t *testing.T) {
+	client := NewClient("https://test.mattermost.com", "bot-token", "pat-token")
+	SetGlobalClient(client)
+	assert.Equal(t, client, GetGlobalClient())
+}