🐞Improve API documentation of POST /contract endpoint

[mkanal]

• Rename endpoint from /contracts to /contract-agreements
• Change description from "All contract agreements for all assets" to "Contract agreements according to particular filter expression"
• Change description from "This endpoint returns all contract agreements for all assets in Trace-X" to "Returns contract agreements according to particular filter expression"
• Change "pageAble" to "pageable"
• Change Operator "EQUAL" to "EQUALS"
• Change "counterpartyAddress" to "counterPartyAddress"
• Change "size" in RBody to "pageSize"