Add a configuration where users can customize the maximum entity size.

[Juliexie2023]

When adding test cases to a test run, if there are too many cases, it will keep showing "updating".

The log as following:
PayloadTooLargeError: request entity too large
at readStream (/app/backend/node_modules/raw-body/index.js:163:17)
at getRawBody (/app/backend/node_modules/raw-body/index.js:116:12)
at read (/app/backend/node_modules/body-parser/lib/read.js:79:3)
at jsonParser (/app/backend/node_modules/body-parser/lib/types/json.js:138:5)
at Layer.handle [as handle_request] (/app/backend/node_modules/express/lib/router/layer.js:95:5)
at trim_prefix (/app/backend/node_modules/express/lib/router/index.js:328:13)
at /app/backend/node_modules/express/lib/router/index.js:286:9
at Function.process_params (/app/backend/node_modules/express/lib/router/index.js:346:12)
at next (/app/backend/node_modules/express/lib/router/index.js:280:10)
at cors (/app/backend/node_modules/cors/lib/index.js:188:7)

Could you add a configuration where users can customize the maximum entity size?