Expand allowedUsers email field to support comma-separated and domains (#9)

* Expand allowedUsers email field to support comma-separated and domains

Closes #8

* Refactor AuthFetch() to return AuthUser struct

Also, this breaks out a parseLine() function which can be easily tested.

* Ignore empty addrs after splitting commas

This ignores a trailing comma

* Add tests for auth parseLine()

* Update documentation in smtprelay.ini

* Fix bug where addrAllowed() was incorrectly case-sensitive

* Update allowedUsers allowed domain format to require leading @

This disambiguates a local user ('john.smith') from a domain ('example.com')

main_test.go

@@ -0,0 +1,94 @@
+package main
+
+import (
+	"testing"
+)
+
+func TestAddrAllowedNoDomain(t *testing.T) {
+	allowedAddrs := []string{"joe@abc.com"}
+	if addrAllowed("bob.com", allowedAddrs) {
+		t.FailNow()
+	}
+}
+
+func TestAddrAllowedSingle(t *testing.T) {
+	allowedAddrs := []string{"joe@abc.com"}
+
+	if !addrAllowed("joe@abc.com", allowedAddrs) {
+		t.FailNow()
+	}
+	if addrAllowed("bob@abc.com", allowedAddrs) {
+		t.FailNow()
+	}
+}
+
+func TestAddrAllowedDifferentCase(t *testing.T) {
+	allowedAddrs := []string{"joe@abc.com"}
+    testAddrs := []string{
+        "joe@ABC.com",
+        "Joe@abc.com",
+        "JOE@abc.com",
+        "JOE@ABC.COM",
+    }
+    for _, addr := range testAddrs {
+        if !addrAllowed(addr, allowedAddrs) {
+            t.Errorf("Address %v not allowed, but should be", addr)
+        }
+    }
+}
+
+func TestAddrAllowedLocal(t *testing.T) {
+	allowedAddrs := []string{"joe"}
+
+	if !addrAllowed("joe", allowedAddrs) {
+		t.FailNow()
+	}
+	if addrAllowed("bob", allowedAddrs) {
+		t.FailNow()
+	}
+}
+
+func TestAddrAllowedMulti(t *testing.T) {
+	allowedAddrs := []string{"joe@abc.com", "bob@def.com"}
+	if !addrAllowed("joe@abc.com", allowedAddrs) {
+		t.FailNow()
+	}
+	if !addrAllowed("bob@def.com", allowedAddrs) {
+		t.FailNow()
+	}
+	if addrAllowed("bob@abc.com", allowedAddrs) {
+		t.FailNow()
+	}
+}
+
+func TestAddrAllowedSingleDomain(t *testing.T) {
+	allowedAddrs := []string{"@abc.com"}
+	if !addrAllowed("joe@abc.com", allowedAddrs) {
+		t.FailNow()
+	}
+	if addrAllowed("joe@def.com", allowedAddrs) {
+		t.FailNow()
+	}
+}
+
+func TestAddrAllowedMixed(t *testing.T) {
+	allowedAddrs := []string{"app", "app@example.com", "@appsrv.example.com"}
+	if !addrAllowed("app", allowedAddrs) {
+		t.FailNow()
+	}
+	if !addrAllowed("app@example.com", allowedAddrs) {
+		t.FailNow()
+	}
+	if addrAllowed("ceo@example.com", allowedAddrs) {
+		t.FailNow()
+	}
+	if !addrAllowed("root@appsrv.example.com", allowedAddrs) {
+		t.FailNow()
+	}
+	if !addrAllowed("dev@appsrv.example.com", allowedAddrs) {
+		t.FailNow()
+	}
+	if addrAllowed("appsrv@example.com", allowedAddrs) {
+		t.FailNow()
+	}
+}