[agroal#392] Add application name and version in management protocol

In order to improve debugging, [agroal#392] suggested to write
the sender application name and its version in the
socket over which pgagroal-cli and pgagroal communicate.

Introduces the 'write_info' function in management.c.

AUTHORS

@@ -11,3 +11,4 @@ Yongting You <2010youy01@gmail.com>
 Ashutosh Sharma <ash2003sharma@gmail.com>
 Henrique de Carvalho <decarv.henrique@gmail.com>
 Yihe Lu <t1t4m1un@gmail.com>
+Eugenio Gigante <giganteeugenio2@gmail.com>

src/include/management.h

@@ -76,6 +76,25 @@ extern "C" {
 #define COMMAND_OUTPUT_FORMAT_TEXT 'T'
 #define COMMAND_OUTPUT_FORMAT_JSON 'J'
 
+/**
+ * Available applications
+ */
+#define PGAGROAL_EXECUTABLE 1
+#define PGAGROAL_EXECUTABLE_CLI 2
+#define PGAGROAL_EXECUTABLE_VAULT 3
+
+/*
+ * stores the application name and its version
+ * which are sent through the socket
+ */
+struct pgagroal_version_info
+{
+   char s[2];
+   int command;
+   char v[3];
+   int version;
+};
+
 /**
  * Get the frontend password of a user
  * @param ssl The SSL connection