Added ability to test the connection in the dialog where the connection details are entered.

pglablib/TestConnection.h

@@ -0,0 +1,32 @@
+#pragma once
+
+#include <QString>
+#include <QStringList>
+
+class ConnectionConfig;
+
+class TestConnectionResult {
+public:
+    /// Creates an instance signalling failure
+    static TestConnectionResult Failed(QString msg);
+    /// Creates a result instance signalling success
+    static TestConnectionResult Success(QStringList databases);
+
+    TestConnectionResult() = default;
+
+    bool ok() const;
+    QString message() const;
+    const QStringList& databases() const;
+private:
+    bool Ok;
+    QString Message;
+    QStringList Databases;
+
+    TestConnectionResult(bool ok, QString msg, QStringList databases);
+};
+
+/// Test if a connection can be opened using the details in cc
+///
+/// It returns either the error message from the string on failure
+/// or a list of databases the details give access to.
+TestConnectionResult TestConnection(const ConnectionConfig &cc);