Data provider simplification, tests, and documentation (#1997)

* Ignore env.test from source control

* Simplification of providers interface

* Synth tests

* Update money to use new find rates method

* Remove unused issues code

* Additional issue feature removals

* Update price data fetching and tests

* Update documentation for providers

* Security test fixes

* Fix self host test

* Update synth usage data access

* Remove AI pr schema changes

app/models/plaid_item/provided.rb

@@ -0,0 +1,26 @@
+module PlaidItem::Provided
+  extend ActiveSupport::Concern
+
+  class_methods do
+    def plaid_us_provider
+      Providers.plaid_us
+    end
+
+    def plaid_eu_provider
+      Providers.plaid_eu
+    end
+
+    def plaid_provider_for_region(region)
+      region.to_sym == :eu ? plaid_eu_provider : plaid_us_provider
+    end
+  end
+
+  private
+    def eu?
+      raise "eu? is not implemented for #{self.class.name}"
+    end
+
+    def plaid_provider
+      eu? ? self.class.plaid_eu_provider : self.class.plaid_us_provider
+    end
+end