Remove custom TSRange parser

This commit removes the custom TSRange parser implemented in Chronomodel
in favor of the standard Rails tsrange parser.

Implementation:
- Keep returning `nil` instead of Infinity values to keep the previous
  behaviour and allow Rails 7.0 to work (ref: rails/rails#45099)
- Check for `Time` because `validity` is a column with `tsrange` type,
  so that only `Time`, `nil`, and Infinity are supposed to be there
- Bump major version because this is a potential breaking change

Motivation:
- Resolved dependencies:
  - Ruby 2.6+ now supports open-ended ranges, addressing the limitation in
    https://bugs.ruby-lang.org/issues/6864
  - Rails tsrange stability issues in rails/rails#13793 and
    rails/rails#14010
- Standardized usage:
  - Aligns Chronomodel with Rails conventions, improving compatibility and
    reducing code complexity.
- Leverage official API:
  - Accesses potential future improvements and bug fixes in the standard
    tsrange.

Considerations:
- Applications relying on validity.last might require migration
  strategies due to open-ended ranges.
- Utilize Chronomodel's validity and valid_from / valid_to for accurate
  handling of open-ended ranges.

Benefits:
- Simplified codebase
- Enhanced Rails compatibility
- Future-proofed against potential API changes

This change strengthens Chronomodel's foundation and paves the way for
seamless integration with the wider Ruby and Rails communities.

Close #269

Ref:
- rails/rails#45099

README.md

@@ -328,10 +328,6 @@ Ensure to run the full test suite before pushing.
    of an object at a specific point in time within the application could
    lead to inaccuracies.
 
- * Rails 4+ support requires disabling tsrange parsing support, as it
-   [is broken][r4-tsrange-broken] and [incomplete][r4-tsrange-incomplete]
-   as of now, mainly due to a [design clash with ruby][pg-tsrange-and-ruby].
-
  * The triggers and temporal indexes cannot be saved in schema.rb. The AR
    schema dumper is quite basic, and it isn't (currently) extensible.
    As we're using many database-specific features, Chronomodel forces the
@@ -412,17 +408,13 @@ This software is Made in Italy :it: :smile:.
 [pg-exclusion-constraints]: https://www.postgresql.org/docs/9.4/sql-createtable.html#SQL-CREATETABLE-EXCLUDE
 [pg-btree-gist]: https://www.postgresql.org/docs/9.4/btree-gist.html
 [pg-comment]: https://www.postgresql.org/docs/9.4/sql-comment.html
-[pg-tsrange-and-ruby]: https://bugs.ruby-lang.org/issues/6864
 [pg-ctes]: https://www.postgresql.org/docs/9.4/queries-with.html
 [pg-cte-optimization-fence]: https://www.postgresql.org/message-id/[email protected]
 [pg-cte-opt-out-fence]: https://www.postgresql.org/message-id/CAHyXU0zpM5+Dsb_pKxDmm-ZoWUAt=SkHHaiK_DBqcmtxTas6Nw@mail.gmail.com
 [pg-json-type]: https://www.postgresql.org/docs/9.4/datatype-json.html
 [pg-json-func]: https://www.postgresql.org/docs/9.4/functions-json.html
 [pg-json-opclass]: https://github.com/ifad/chronomodel/blob/master/sql/json_ops.sql
 
-[r4-tsrange-broken]: https://github.com/rails/rails/pull/13793#issuecomment-34608093
-[r4-tsrange-incomplete]: https://github.com/rails/rails/issues/14010
-
 [cm-readme-sql]: https://github.com/ifad/chronomodel/blob/master/README.sql
 [cm-timemachine]: https://github.com/ifad/chronomodel/blob/master/lib/chrono_model/time_machine.rb
 [cm-cte-impl]: https://github.com/ifad/chronomodel/commit/18f4c4b

lib/chrono_model/adapter.rb

@@ -7,7 +7,6 @@
 
 require 'chrono_model/adapter/ddl'
 require 'chrono_model/adapter/indexes'
-require 'chrono_model/adapter/tsrange'
 require 'chrono_model/adapter/upgrade'
 
 module ChronoModel
@@ -19,7 +18,6 @@ class Adapter < ActiveRecord::ConnectionAdapters::PostgreSQLAdapter
     include ChronoModel::Adapter::Migrations
     include ChronoModel::Adapter::DDL
     include ChronoModel::Adapter::Indexes
-    include ChronoModel::Adapter::TSRange
     include ChronoModel::Adapter::Upgrade
 
     # The schema holding current data

lib/chrono_model/time_machine/history_model.rb

@@ -209,12 +209,21 @@ def record # :nodoc:
         current_version
       end
 
+      # Return `nil` instead of -Infinity/Infinity to preserve current
+      # Chronomodel behaviour and avoid failures with Rails 7.0 and
+      # unbounded time ranges
+      #
+      # Check if `begin` and `end` are `Time` because validity is a `tsrange`
+      # column, so it is either `Time`, `nil`, and in some cases Infinity.
+      #
+      # Ref: rails/rails#45099
+      # TODO: consider removing when Rails 7.0 support will be dropped
       def valid_from
-        validity.first
+        validity.begin if validity.begin.is_a?(Time)
       end
 
       def valid_to
-        validity.last
+        validity.end if validity.end.is_a?(Time)
       end
       alias as_of_time valid_to
 

lib/chrono_model/version.rb

@@ -1,5 +1,5 @@
 # frozen_string_literal: true
 
 module ChronoModel
-  VERSION = '3.0.1'
+  VERSION = '4.0.0'
 end