springdoc-openapi v1.2.28 released!

Changed

• Upgrade to spring-boot to 2.2.4.RELEASE
• Upgrade swagger-api to 2.1.1
• Upgrade swagger-ui to 3.24.3
• #359 - Make spring-security-oauth2 as optional for springdoc-openapi-security
• #354 - Improve support of response of responses overloading