dev-libs/aws-sdk-cpp: Added explanation of http and full use flags

- http: If ON, prevents the default platform-specific HTTP client from being built into the library.
        If ON, you will need to provide your own platform-specific HTTP client implementation.
- full: Adds access to all supported services.
        This use flag is provided for users who want all features enabled.
        Enabling this will increase build times significantly.
        (around 30 minutes build time when compiling with 16 threads on a Ryzen 9 7900).

Signed-off-by: KotoishiHeart <trakrailysurely@danceylove.net>

dev-libs/aws-sdk-cpp/metadata.xml

@@ -6,6 +6,7 @@
     <name>Okamura Kazuya</name>
   </maintainer>
   <use>
+    <flag name="http">If ON, prevents the default platform-specific HTTP client from being built into the library. If ON, you will need to provide your own platform-specific HTTP client implementation.</flag>
     <flag name="storage">Adds access to services related to object, block, and file storage.</flag>
     <flag name="compute">Adds access to Compute and Auto Scaling related services.</flag>
     <flag name="networking">Adds access to network and CDN related services.</flag>
@@ -20,6 +21,7 @@
     <flag name="devops">Adds access to CI/CD and developer related services.</flag>
     <flag name="mgmt">Adds access to operational management related services.</flag>
     <flag name="other">Add access to services that do not easily fit into existing groups.</flag>
+    <flag name="full">Adds access to all supported services. Enabling this will significantly increase build times.</flag>
   </use>
   <upstream>
     <remote-id type="github">aws/aws-sdk-cpp</remote-id>