support schema files from third-party plugins

Allow upgrade process to include schema files from third-party plugins
installed in /usr/share/ipa/schema.d/*.schema.

The directory /usr/shar/eipa/schema.d is owned by the server-common
subpackage and therefore third-party plugins should depend on
freeipa-server-common (ipa-server-common) package in their package
dependencies.

Resolves: https://fedorahosted.org/freeipa/ticket/5864
Reviewed-By: Martin Basti <mbasti@redhat.com>

install/share/Makefile.am

@@ -3,6 +3,7 @@ NULL =
 SUBDIRS =  				\
 	advise				\
 	profiles			\
+	schema.d			\
 	$(NULL)
 
 appdir = $(IPA_DATA_DIR)

install/share/schema.d/Makefile.am

@@ -0,0 +1,16 @@
+NULL =
+
+SUBDIRS =  				\
+	$(NULL)
+
+appdir = $(IPA_DATA_DIR)/schema.d
+app_DATA = README			\
+	$(NULL)
+
+EXTRA_DIST =				\
+	$(app_DATA)			\
+	$(NULL)
+
+MAINTAINERCLEANFILES =			\
+	*~				\
+	Makefile.in

install/share/schema.d/README

@@ -0,0 +1,14 @@
+This directory is indended to store schema files for 3rd-party plugins.
+
+Each schema file should be named NN-description.ldif where NN is a number 00..90.
+
+The schema files from this directory are merged together with the core IPA
+schema files during the run of ipa-server-upgrade utility. Therefore, they are
+also installed when upgrade happens within the process of ipa-server-install.
+
+The directory is installed as /usr/share/ipa/schema.d and is owned by a
+freeipa-server-common package. Therefore, a 3rd-party plugin would need to
+depend on the freeipa-server-common package if it delivers the schema file(s).
+
+You may place your schema files in a subdirectory too, the code that loads
+schema files processes recursively all subdirectories of schema.d.