Allow ddb devutils client override

refs FOO-925

Change-Id: I24e54c5afa0f2230b63c90c470d5c59dfdabbccb
Reviewed-on: https://gerrit.instructure.com/c/canvas-lms/+/246806
Tested-by: Service Cloud Jenkins <svc.cloudjenkins@instructure.com>
Reviewed-by: Michael Ziwisky <mziwisky@instructure.com>
QA-Review: Michael Ziwisky <mziwisky@instructure.com>
Product-Review: Michael Ziwisky <mziwisky@instructure.com>

config/vault_contents.yml.example

@@ -6,12 +6,12 @@
 # shaped like the example below.  Each environment can get a hash,
 # there's a key for each read path, and a hash for the returned data
 development:
-  'sts/testaccount/sts/canvas-shards-lookuper-dev':
+  'sts/testaccount/sts/canvas-shards-lookupper-dev':
     access_key: 'fake-access-key'
     secret_key: 'fake-secret-key'
     security_token: 'fake-security-token'
 test:
-  'sts/testaccount/sts/canvas-shards-lookuper-test':
+  'sts/testaccount/sts/canvas-shards-lookupper-test':
     access_key: 'fake-access-key'
     secret_key: 'fake-secret-key'
     security_token: 'fake-security-token'

lib/canvas/dynamo_db/dev_utils.rb

@@ -31,11 +31,11 @@ module Canvas
         }
       }.freeze
 
-      def self.initialize_ddb_for_development!(category, table_name, recreate: false, schema: nil)
+      def self.initialize_ddb_for_development!(category, table_name, recreate: false, schema: nil, ddb: nil)
         unless ["development", "test"].include?(Rails.env)
           raise "DynamoDB should not be initialized this way in a real environment!!!"
         end
-        canvas_ddb = Canvas::DynamoDB::DatabaseBuilder.from_config(category)
+        canvas_ddb = ddb || Canvas::DynamoDB::DatabaseBuilder.from_config(category)
         dynamodb = canvas_ddb.client
         local_table_name = canvas_ddb.prefixed_table_name(table_name)
         exists = begin