Sync: merge releases 2.2.3 and onward from ncbo

[jvendetti]

The purpose of this pull request is to merge all of the code from releases 2.2.5 through 2.4.0 from the ncbo/ontologies_api_ruby_client sub-fork. It also contains a re-merge of code from releases 2.2.3 and 2.2.4 with a regular merge commit, instead of a squash and merge.

To follow are slightly abbreviated release notes for the aforementioned releases:

2.4.0

• Adopt some of the optimizations implemented by our LIRMM collaborators in their version of this library.

2.3.0

• Add multiple media types models

2.2.5

• Upgrade activesupport from 6.1.7.3 to 7.0.8
• Bump minitest from 5.18 to 5.20
• Add minitest-hooks as a development dependency
• Validate provided API key before executing the unit test suite
• Remove Ruby 2.7 and add 3.1 to the test matrix
• Run unit tests in verbose mode
• Update gemspec description and README to include the AllegroGraph database

2.2.4

• Replace outdated test-unit with minitest

2.2.3

• Modified the purl method to check class IDs for a PURL host, rather than the string 'purl'
• Made the PURL host configurable, and set a default value
• Added several unit tests for the purl method
• Configured PURL host and prefix values in config.test.rb for the purposes of unit text execution
• Added a development dependency on the faraday-follow_redirects gem for testing proper PURL resolution
• Moved the gem version specifier to a module
• Fixed some RuboCop warnings
• Synced fork with the upstream repository