… methods

This change deprecates most GraphService.PostAsync and GraphService.SendAsync methods, of which there were at least six total. It introduces two new GraphService.PostAsync methods to replace them all, which standardize the usage of the `GraphRequest` class and serializing all requests to json.

Previously, some of the PostAsync/SendAsync methods would serialize the request to json, some wouldn't. Some would send the variables, some wouldn't. Some would let you set your own json wherein you could apply the variables yourself, but then they'd send the `application/graphql` content-type, which made Shopify ignore any variables sent.

…dGraphResponse class for deserializing GraphQL responses

Changes:

- Introduced a new class named `ParsedGraphResponse<T>` to be used for deserializing Shopify's GraphQL responses. It includes two properties: `Data` of type `T` and `UserErrors` of type `ICollection<UserError>`.
- Modified the error handling logic in `GraphService` to use the new `ParsedGraphResponse<T>` class.
- Refactored all public methods in `GraphService` to use the same internal method for calling the GraphQL API. Tests will be added to ensure the obsoleted methods have not been broken.
- Deprecated `GraphService.CheckForErrors<T>`

Type: feature

… JsonSerializerOptions

Planning to use a camel case property name strategy with System.Text.Json instead.

Type: fix

Type: chore

Type: chore

…ing for userErrors

Worried about too much memory usage/potential memory leaks by using JsonElement for unknown, potentially gigantic json values in an exception.

…lizerOptions