Feature: add warnings for deprecated methods

[mrcromero]

Currently, deprecation appears in ruby only via a comment in the associated method. However, since this isn't explicit on the client-side, deprecation might silently be missed, and dropping of endpoints/methods may come without warning.

Description
This creates a deprecation helper-module to emit warnings for deprecated methods + updates generation templates to use it. Library has been regenerated, tests added, updated README. Additionally, added YARD metadata tags -> helps IDEs identify the methods as deprecated.

Though rubygems has Gem::Deprecate for this functionality, it's designed for warning and then delegating to an alternative, which doesn't fit this libraries' use-case. I also wanted the warning to exhibit the same information as the existing comment (deprecation version, point to alternative API) which the former doesn't support.

Additional notes:

• It's in the README as well: deprecation warnings are hidden by default in Ruby, but also included knobs to disable only this library's warnings:
  • Adyen::Deprecation.silenced = true in the Ruby app
  • or setting env variable ADYEN_SILENCE_DEPRECATIONS to 1, true, or yes
• posTerminalManagement.rb and hmac_validator.rb had some deprecated code that wasn't updated after generation because the former is out of the generation list (deprecated API) and the latter is manual code. Updated both manually.
• There's an extra workaround to support older versions of ruby (ruby 2.7 doesn't support emitting warnings with categories, that's what CATEGORY_SUPPORT is for). If we decide to move along with 3.3+, then this can be dropped.

Example of what the warnings will look like to the user:

/tmp/deprecation_user_view.rb:18: warning: [DEPRECATED] `origin_keys` is deprecated since Adyen Checkout API v67

Tested scenarios

• Tested one deprecated: that the warning is emitted but the call still succeeds
• Tested formatting, logic of deprecation-helper, and that a warning appears

[gemini-code-assist]

Code Review

This pull request introduces a deprecation warning mechanism for deprecated API methods, updating the Mustache templates to automatically generate deprecation warnings and updating several API clients accordingly. The review feedback suggests avoiding Gem::Version for Ruby version checks to eliminate unnecessary RubyGems dependencies, and recommends using Kernel.warn instead of calling Warning.warn directly to ensure custom warning handlers are respected.

[gcatanese]

Great work, both solution and documentation. I found one potential problem, pls have a look. Thanks

[sonarqubecloud]

Quality Gate passed

Issues
5 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

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