CMake: systematically use the feature-summary

There's not much point in having a feature summary that will
trip over just-a-few of the required packages, while also
using REQUIRED in find_package() calls -- then you have to
re-run CMake for all the REQUIRED ones you're missing,
and then one more time for the packages that are required
in the feature summary.

Use the feature summary (e.g. TYPE REQUIRED) consistently.
Then you can run CMake once and learn about all the missing
dependencies in one go.

CMakeLists.txt

@@ -32,14 +32,38 @@ ecm_setup_version(1.0.80
     VERSION_HEADER ${CMAKE_CURRENT_BINARY_DIR}/neochat-version.h
 )
 
-find_package(Qt5 ${QT_MIN_VERSION} REQUIRED NO_MODULE COMPONENTS Widgets Core Quick Gui QuickControls2 Multimedia Svg)
-find_package(KF5 ${KF5_MIN_VERSION} REQUIRED COMPONENTS Kirigami2 I18n Notifications Config CoreAddons)
+find_package(Qt5 ${QT_MIN_VERSION} NO_MODULE COMPONENTS Widgets Core Quick Gui QuickControls2 Multimedia Svg)
+set_package_properties(Qt5 PROPERTIES
+    TYPE REQUIRED
+    PURPOSE "Basic application components"
+)
+find_package(KF5 ${KF5_MIN_VERSION} COMPONENTS Kirigami2 I18n Notifications Config CoreAddons)
+set_package_properties(KF5 PROPERTIES
+    TYPE REQUIRED
+    PURPOSE "Basic application components"
+)
+set_package_properties(KF5Kirigami2 PROPERTIES
+    TYPE REQUIRED
+    PURPOSE "Kirigami application UI framework"
+)
 
 if(ANDROID)
-    find_package(OpenSSL REQUIRED)
+    find_package(OpenSSL)
+    set_package_properties(OpenSSL PROPERTIES
+        TYPE REQUIRED
+        PURPOSE "Encrypted communications"
+    )
 else()
-    find_package(Qt5Keychain REQUIRED)
-    find_package(KF5DBusAddons ${KF5_MIN_VERSION} REQUIRED)
+    find_package(Qt5Keychain)
+    set_package_properties(Qt5Keychain PROPERTIES
+        TYPE REQUIRED
+        PURPOSE "Secure storage of account secrets"
+    )
+    find_package(KF5DBusAddons ${KF5_MIN_VERSION})
+    set_package_properties(KF5DBusAddons PROPERTIES
+        TYPE REQUIRED
+        PURPOSE "DBus convenience functions"
+    )
 endif()
 
 find_package(Quotient 0.7)