meson: adjust nlohmann-json dependency

Simplify nlohmann-json dependency logic and use wrap file name aligned
with other repositories.

Signed-off-by: Patrick Williams <patrick@stwcx.xyz>
Change-Id: Ie6082726a567e0876e5f8b9d941ed1101e056d2f
diff --git a/meson.build b/meson.build
index 075cddc..7953560 100644
--- a/meson.build
+++ b/meson.build
@@ -50,23 +50,11 @@
 sources = []
 deps = []
 if get_option('associations').allowed()
-    cpp = meson.get_compiler('cpp')
-    if cpp.has_header('nlohmann/json.hpp')
-        nlohmann_json_dep = declare_dependency()
-    else
-        subproject('nlohmann', required: false)
-        nlohmann_json_dep = declare_dependency(
-            include_directories: [
-                'subprojects/nlohmann/single_include',
-                'subprojects/nlohmann/single_include/nlohmann',
-            ]
-        )
-    endif
     sources += [
         'association_manager.cpp',
     ]
     deps += [
-        nlohmann_json_dep,
+        dependency('nlohmann_json', include_type: 'system'),
     ]
 endif
 
diff --git a/subprojects/nlohmann.wrap b/subprojects/nlohmann_json.wrap
similarity index 60%
rename from subprojects/nlohmann.wrap
rename to subprojects/nlohmann_json.wrap
index 0fd7c06..3745380 100644
--- a/subprojects/nlohmann.wrap
+++ b/subprojects/nlohmann_json.wrap
@@ -1,3 +1,6 @@
 [wrap-git]
+revision = HEAD
 url = https://github.com/nlohmann/json.git
-revision = HEAD
\ No newline at end of file
+
+[provide]
+nlohmann_json = nlohmann_json_dep