feat: Always use POST to normalize request serialization

[razor-x]

This intention is for GET to be used when possible, but blocking issues mean we need to use POST until we can ensure consistent request serialization and parsing for the query string.

[seveibar]

whats the motivation here? (I agree w/ it fwiw- GET is an optimization we don't need atm)

[sybohy]

@seveibar motivation: https://hello-seam.slack.com/archives/C01D0J9ACLF/p1698670175221979

[razor-x]

For all those who cannot see internal Slack threads, here are the details on this change.

1. All SDKs are moving to generated form. Until this nexlove issue is resolved, all the generated SDK will only use POST (since they don't have access to GET in the openapi spec): OpenAPI spec missing get when post is defined nextlove#117
2. Seam fully intends to prefer GET in the SDK and docs when GET is properly supported.
3. (2) is not ready yet due to some blocking issues:

• (1) as noted above.
• Serialization / parsing of array params. All SDKs need to implement a consistent serializer. (This serializer could be used as a reference model https://github.com/seamapi/javascript-http/blob/main/src/lib/params-serializer.ts). And this issue needs to be addressed Support all array query serializations  nextlove#77