[MINOR FEATURE]: Capture ApodiniError/@Throws in the `APIDocument`

[Supereg]

Problem

As of now, the Migrator InterfaceExporter won't index the Apodini web service defined ApodiniErrors. Instead it uses a standard set of default ErrorCodes.

Solution

Parse @Throws declarations inside a Handler in the ApdoniMigratorInterfaceExporter and properly build the APIDocument. Additionally, changes in error codes should be captured by the MigrationGuide.

Additional context

Ideally, the RESTMigrator would be updated to adjust for the updated error code definitions. This issue does not require to come up with a meaningful way of handling error migrations.

• relates to #6

Code of Conduct

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