Increase upload file size limit to support large Postman collection

[lbroudoux]

As of today, Spring Boot properties that controls upload file size are not tuned. So we have:

spring.servlet.multipart.max-file-size=1MB
spring.servlet.multipart.max-request-size=10MB

Whilst max request size seems fairly enough, max file size can be a bit small to handle large Postman collection files. We propose to increase this setting to 2MB by default in Microcks and allow override through an environment variable that could be setup by Helm chart or Operator if provided at installation time.