Manually added missing mergefieldinfo to AgreementInfo model

[ivanah-aliya]

Description

Manually added missing mergefieldinfo to AgreementInfo model to allow populating fields using the createAgreement API:
https://secure.na2.echosign.com/public/docs/restapi/v6#!/agreements/createAgreement

Added attribute:

mergeFieldInfo (MergefieldInfo[], optional): Optional default values for fields to merge into the document. The values will be presented to the signers for editable fields; for read-only fields the provided values will not be editable during the signing process. Merging data into fields is currently not supported when used with libraryDocumentId or libraryDocumentName. Only file and url are currently supported,

Related Issue

https://github.com/adobe-sign/AdobeSignJavaSdk/issues/11
Please update AgreementInfo model to include mergefieldinfo

Motivation and Context

Without this change, adding mergeFields to dynamically populate form fields in a library document template when calling the createAgreement API wouldn't be possible.

How Has This Been Tested?

Used this in our code base and we were able to add data to mergeFields successfully.

Screenshots (if appropriate):

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• I have signed the Adobe Open Source CLA.
• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• All new and existing tests passed.