ARROW-17864: [Plasma][Ruby] Deprecate Plasma Ruby bindings (apache#14258)

See discussion at
https://lists.apache.org/thread/nw232k2lzmg9kcl8ts475m9ybl34j81p

Authored-by: Sutou Kouhei <[email protected]>
Signed-off-by: Sutou Kouhei <[email protected]>

Author: kou

ruby/README.md

@@ -29,7 +29,7 @@ Here are the official Ruby bindings for Apache Arrow.
 
 [Red Gandiva](https://github.com/apache/arrow/tree/master/ruby/red-gandiva) is the Gandiva bindings.
 
-[Red Plasma](https://github.com/apache/arrow/tree/master/ruby/red-plasma) is the Plasma bindings.
+[Red Plasma](https://github.com/apache/arrow/tree/master/ruby/red-plasma) is the Plasma bindings. (This is deprecated since 10.0.0. This will be removed from 12.0.0 or so.)
 
 [Red Parquet](https://github.com/apache/arrow/tree/master/ruby/red-parquet) is the Parquet bindings.
 

ruby/red-plasma/README.md

@@ -19,6 +19,8 @@
 
 # Red Plasma - Plasma Ruby
 
+This is deprecated since 10.0.0. This will be removed from 12.0.0 or so.
+
 Red Plasma is the Ruby bindings of Plasma. Red Plasma is based on GObject Introspection.
 
 Plasma is an in-memory object store and cache for big data.

ruby/red-plasma/red-plasma.gemspec

@@ -33,7 +33,12 @@ Gem::Specification.new do |spec|
   spec.email = ["[email protected]"]
 
   spec.summary = "Red Plasma is the Ruby bindings of Plasma"
-  spec.description = "Plasma is an in-memory object store and cache for big data."
+  deprecated_message =
+    "red-plasma is deprecated since 10.0.0. " +
+    "red-plasma will not be released from Apache Arrow 12.0.0 or so."
+  spec.description =
+    "Plasma is an in-memory object store and cache for big data. " +
+    deprecated_message
   spec.license = "Apache-2.0"
   spec.files = ["README.md", "Rakefile", "Gemfile", "#{spec.name}.gemspec"]
   spec.files += ["LICENSE.txt", "NOTICE.txt"]
@@ -46,4 +51,6 @@ Gem::Specification.new do |spec|
   spec.add_development_dependency("bundler")
   spec.add_development_dependency("rake")
   spec.add_development_dependency("test-unit")
+
+  spec.post_install_message = deprecated_message
 end