Bump several dependencies and misc refactor

[arvindkrishnakumar-okta]

Issue(s)

• Several outdated dependencies #990
• Recommendation from OpenAPI spec missing some default role type #993 (comment) (Thanks @clementdenis) - set enumUnknownDefaultCase config in openapi-generator to true.
• Bump openapi generator from 6.6.0 to 7.4.0 (this causes some previously unused/incorrectly generated models to be removed in new generation and hence this causes a major change in versioning, also this upgrade requires Java 11+).
• Cleaned up unused spring-web and spring-retry dependencies
• Bump jknack.handlebars from 4.3.1 to 4.4.0
• Bump jackson from 2.15.3 to 2.17.0
• Bump bouncy castle from 1.76 to 1.77
• Bump jjwt from 0.11.5 to 0.12.5
• Bump httpclient5 from 5.2.1 to 5.3.1
• Bump okta commons from 1.3.3 to 1.3.5
• Updated README to note Java 11 as the prerequisite for using this SDK (was Java 8 earlier).

Description

Category

• Bugfix
• Enhancement
• New Feature
• Library Upgrade
• Configuration Change
• Versioning Change
• Unit or Integration Test(s)
• Documentation

Signoff

• I have submitted a CLA for this PR
• Each commit message explains what the commit does
• I have updated documentation to explain what my PR does
• My code is covered by tests if required
• I did not edit any automatically generated files