* fix json code block in kv api docs
* add custom_metadata to GET, PUT, PATCH in kv api docs
* add custom_metadata to get, put, and patch in kv CLI docs
* add custom-metdata flag to "kv metadata put" command
* add kv metadata put command test for custom-metadata flag
* add custom_metadata to kv-v2 api docs
* add custom_metadata to kv-v2 cli docs
* update go.mod
* Add custom metadata limits to docs
* add changelog entry
* update vault-plugin-secrets-kv to @master
Just a suggestion on how to perhaps improve the language as I found myself re-reading the sentences due to the missing "either ... or ..." having been _told_ that it `can be run in two modes`.