[New] Add sendMail hook in subscription

Added sendMail hook in subscription, before a mail is sent to confirm a
subscription. It makes it more flexible for modules to interact with it.

htdocs/adherents/subscription.php

@@ -300,6 +300,23 @@ if ($user->rights->adherent->cotisation->creer && $action == 'subscription' && !
 		if (!$error) {
 			// Send confirmation Email
 			if ($object->email && $sendalsoemail) {   // $object is 'Adherent'
+				$parameters = array(
+					'datesubscription' => $datesubscription,
+					'amount' => $amount,
+					'ccountid' => $accountid,
+					'operation' => $operation,
+					'label' => $label,
+					'num_chq' => $num_chq,
+					'emetteur_nom' => $emetteur_nom,
+					'emetteur_banque' => $emetteur_banque,
+					'datesubend' => $datesubend
+				);
+				$reshook = $hookmanager->executeHooks('sendMail', $parameters, $object, $action); // Note that $action and $object may have been modified by some hooks
+				if ($reshook < 0) {
+					setEventMessages($hookmanager->error, $hookmanager->errors, 'errors');
+				}
+
+				if (empty($reshook)) {
 					$subject = '';
 					$msg = '';
 
@@ -352,6 +369,7 @@ if ($user->rights->adherent->cotisation->creer && $action == 'subscription' && !
 					} else {
 						setEventMessages($langs->trans("EmailSentToMember", $object->email), null, 'mesgs');
 					}
+				}
 			} else {
 				setEventMessages($langs->trans("NoEmailSentToMember"), null, 'mesgs');
 			}