feat: add db.operation attribute for dalli (#458)

Author: ericmustin

instrumentation/dalli/lib/opentelemetry/instrumentation/dalli/patches/server.rb

@@ -14,6 +14,7 @@ def request(op, *args) # rubocop:disable Naming/MethodParameterName
             operation = Utils.opname(op, multi?)
             attributes = {
               'db.system' => 'memcached',
+              'db.operation' => operation,
               'net.peer.name' => hostname,
               'net.peer.port' => port
             }

instrumentation/dalli/test/opentelemetry/instrumentation/dalli/instrumentation_test.rb

@@ -50,6 +50,7 @@
       _(span.name).must_equal 'set'
       _(span.attributes['db.system']).must_equal 'memcached'
       _(span.attributes['db.statement']).must_equal 'set foo bar 0 0'
+      _(span.attributes['db.operation']).must_equal 'set'
       _(span.attributes['net.peer.name']).must_equal host
       _(span.attributes['net.peer.port']).must_equal port
     end
@@ -61,6 +62,7 @@
       _(span.name).must_equal 'get'
       _(span.attributes['db.system']).must_equal 'memcached'
       _(span.attributes['db.statement']).must_equal 'get foo'
+      _(span.attributes['db.operation']).must_equal 'get'
       _(span.attributes['net.peer.name']).must_equal host
       _(span.attributes['net.peer.port']).must_equal port
     end
@@ -72,6 +74,7 @@
       _(span.name).must_equal 'getkq'
       _(span.attributes['db.system']).must_equal 'memcached'
       _(span.attributes['db.statement']).must_equal 'getkq foo bar'
+      _(span.attributes['db.operation']).must_equal 'getkq'
       _(span.attributes['net.peer.name']).must_equal host
       _(span.attributes['net.peer.port']).must_equal port
     end
@@ -93,6 +96,7 @@
       _(span.name).must_equal 'getkq'
       _(span.attributes['db.system']).must_equal 'memcached'
       _(span.attributes['db.statement']).must_equal 'getkq foo bar'
+      _(span.attributes['db.operation']).must_equal 'getkq'
       _(span.attributes['net.peer.name']).must_equal host
       _(span.attributes['net.peer.port']).must_equal port