chore(deps): update Rails dependencies

[dex-the-ai]

Summary

• Updates the Rails dependency constraint from ~> 7.1.3, >= 7.1.3.2 to ~> 8.1.3, >= 8.1.3.1.
• Adds a conservative json < 3.0 compatibility pin because the current rswag/json-schema validation path still uses the json 2.x parse API.
• Keeps the full request-suite validation stable on Rails 8 by making Swagger request specs use isolated test document IDs, align delete responses with the API's 202 Accepted, allow nullable airline callsigns from travel-sample, and return 400 Bad Request for invalid airport/route create payloads.

Dependency updates

Ecosystem	Dependency	Previous	Updated	Type	Notes
Ruby/Bundler	rails	~> 7.1.3, >= 7.1.3.2	~> 8.1.3, >= 8.1.3.1	direct runtime	Latest stable Rails resolved by Bundler under Ruby 3.4.1.
Ruby/Bundler	json	unconstrained transitive/default resolution	< 3.0	compatibility pin	Required until current rswag/json-schema stack supports json 3.x parse keywords/arity.

Validation

Commands run locally with Ruby 3.4.1 via the official Docker image, using a local Couchbase Server container with travel-sample loaded and redacted DB_CONN_STR/DB_USERNAME/DB_PASSWORD values mapped to the app's expected env vars:

bundle install
ruby -c app/controllers/api/v1/airports_controller.rb
ruby -c app/controllers/api/v1/routes_controller.rb
ruby -c spec/requests/swagger/airlines_spec.rb
ruby -c spec/requests/swagger/airports_spec.rb
ruby -c spec/requests/swagger/routes_spec.rb
bundle exec rails runner 'puts defined?(COUCHBASE_CLUSTER) && COUCHBASE_CLUSTER ? :connected : :not_connected'
bundle exec rspec spec/requests
bundle exec rspec spec/requests/api/v1
bundle exec rake rswag:specs:swaggerize

Results:

• bundle exec rspec spec/requests: 64 examples, 0 failures.
• bundle exec rspec spec/requests/api/v1: 27 examples, 0 failures.
• bundle exec rake rswag:specs:swaggerize: generated swagger/v1/swagger.yaml, 64 examples, 0 failures in dry-run documentation generation.
• Couchbase smoke check printed connected before the request-suite run.

Evidence

Reviewer media captured against the running Rails app at /api-docs plus an API smoke request to /api/v1/airports/airport_1262.

Swagger UI screenshot

API smoke screenshot

Walkthrough video

Open the UI/API walkthrough

Local trace copies:

• /home/ubuntu/.hermes/kanban/boards/couchbase-examples/workspaces/t_181a35ff/repo/.hermes/evidence/screenshots/swagger-api-docs.png
• /home/ubuntu/.hermes/kanban/boards/couchbase-examples/workspaces/t_181a35ff/repo/.hermes/evidence/screenshots/api-smoke-airport.png
• /home/ubuntu/.hermes/kanban/boards/couchbase-examples/workspaces/t_181a35ff/repo/.hermes/evidence/video/ui-walkthrough.webm

Existing dependency PR context

• Overlaps Dependabot PR Update rails requirement from ~> 7.1.3, >= 7.1.3.2 to ~> 8.1.3 in the rails group across 1 directory #11 for the Rails 8 dependency constraint. This Hermes PR intentionally includes local Couchbase-backed validation and compatibility fixes.
• Dependabot PR Bump actions/checkout from 6 to 7 #16 updates actions/checkout and is unrelated to the Bundler dependency update here.

Risk notes

• Rails 8 is a major framework update; this PR includes only the minimum app/spec compatibility changes needed for the existing validation surface.
• json < 3.0 is intentionally constraint-limited to preserve current rswag/json-schema compatibility. It can be revisited once that stack supports json 3.x.
• Gemfile.lock is ignored by this repository and was not committed, preserving the repository's existing lockfile convention.

Rollback

Revert this PR to restore the previous Rails constraint, remove the json compatibility pin, and return the Swagger/API compatibility changes to their prior behavior.

Hermes task

Kanban task: t_181a35ff