Add enum values to config properties docs

[abelsromero]

We recently looked into pool configurations and found references to configuration values not in the docs.
This PR simply adds the enum values so there's no need to look into the code.
Updated

• httpclient.pool.leasing-strategy
• httpclient.pool.type
• httpclient.proxy.type

[spencergibb]

These should go in the configprops class or metadata file as this will be overwritten by a build

[abelsromero]

Thanks, updated the JavaDocs in the source class.