Drop support to Ruby 2.6 and Rails 6.0

We aren't testing against those anymore, so we don't support them anymore.

Author: rafaelfranca

.rubocop.yml

@@ -8,13 +8,9 @@ plugins:
   - rubocop-rails
 
 AllCops:
-  TargetRubyVersion: 2.6
+  TargetRubyVersion: 2.7
   DisabledByDefault: true
 
-Rails/IndexBy:
-  Enabled: false # until we support Rails version 6.0
-
-# Prefer assert_not over assert !
 Rails/AssertNot:
   Include:
     - '**/test/**/*'

activeresource.gemspec

@@ -27,10 +27,10 @@ Gem::Specification.new do |s|
   s.files = Dir["MIT-LICENSE", "README.md", "lib/**/*"]
   s.require_path = "lib"
 
-  s.required_ruby_version = ">= 2.6.0"
+  s.required_ruby_version = ">= 2.7.0"
 
-  s.add_dependency("activesupport", ">= 6.0")
-  s.add_dependency("activemodel", ">= 6.0")
+  s.add_dependency("activesupport", ">= 7.0")
+  s.add_dependency("activemodel", ">= 7.0")
   s.add_dependency("activemodel-serializers-xml", "~> 1.0")
 
   s.add_development_dependency("rake")