Changes to Next difficulty adjustment

added the non-success response with the status 500

added the optional property meta/stale_since to the response with the 200 status

added the optional property meta/data_age_days to the response with the 200 status

added the optional property meta/notes to the response with the 200 status

added the optional property meta/period to the response with the 200 status

the response property data/difficultyChange became optional for the status 200

the response property data/estimatedRetargetDate became optional for the status 200

the response property data/nextRetargetHeight became optional for the status 200

the response property data/previousRetarget became optional for the status 200

the response property data/previousTime became optional for the status 200

the response property data/progressPercent became optional for the status 200

the response property data/remainingBlocks became optional for the status 200

the response property data/remainingTime became optional for the status 200

the response property data/timeAvg became optional for the status 200

the response property data/timeOffset became optional for the status 200

response property data/difficultyChange list-of-types was widened by adding types integer and null to media type application/json of response 200

response property data/estimatedRetargetDate list-of-types was widened by adding types null and number to media type application/json of response 200

response property data/nextRetargetHeight list-of-types was widened by adding types null and number to media type application/json of response 200

response property data/previousRetarget list-of-types was widened by adding types integer and null to media type application/json of response 200

response property data/previousTime list-of-types was widened by adding types null and number to media type application/json of response 200

response property data/progressPercent list-of-types was widened by adding types integer and null to media type application/json of response 200

response property data/remainingBlocks list-of-types was widened by adding types null and number to media type application/json of response 200

response property data/remainingTime list-of-types was widened by adding types null and number to media type application/json of response 200

response property data/timeAvg list-of-types was widened by adding types null and number to media type application/json of response 200

response property data/timeOffset list-of-types was widened by adding types null and number to media type application/json of response 200

added the optional property code to the response with the 401 status

added the optional property code to the response with the 429 status

added the optional property code to the response with the 503 status

added the optional property hint to the response with the 401 status

added the optional property hint to the response with the 429 status

added the optional property hint to the response with the 503 status

added the optional property plan to the response with the 401 status

added the optional property plan to the response with the 429 status

added the optional property plan to the response with the 503 status

added the optional property reason to the response with the 401 status

added the optional property reason to the response with the 429 status

added the optional property reason to the response with the 503 status