Given how useful it is to generate dynamic secrets with Vault, I wanted to extend that to my usage of Minio and B2, so writing a secrets engine plugin for Vault has been on my project list for quite some time. A couple weeks ago I came across David Adams's Sample Vault Secrets Plugin, and after about an hour of staring at that and the Vault source, everything clicked and I started writing plugins.
It's a testament to the contributors to Vault that the plugins system is very well thought out and incredibly easy to use, making it a rather simple task to extend Vault. You can find both of mine on GitHub:
Full Disclosure:At the time that this post was written, I am a HashiCorp employee, although this post and the plugins were written as a personal project and are not official HashiCorp products. The views expressed in this posting are entirely personal and are not statements made on the behalf of HashiCorp, Inc.