[FormRecognizer] Parse operation IDs with regex

Summary

The implementation of the Operation constructors uses some magic numbers when parsing the operation ID.

Operations to address

• CopyModelOperation
• RecognizeContentOperation
• RecognizeCustomFormsOperation
• RecognizeReceiptsOperation
• RecognizeIdDocumentsOperation
• TrainingOperation
• AnalyzeDocumentOperation
• ClassifyDocumentOperation

Internal constructor

https://github.com/Azure/azure-sdk-for-net/blob/e32b2e7f7fab4d7209da788250caa2c145b23c66/sdk/formrecognizer/Azure.AI.FormRecognizer/src/RecognizeCustomFormsOperation.cs#L78-L83

The internal constructor takes a parameter called operationLocation, which is returned from the service and is expected to look like:

{endpoint}/formrecognizer/{version}/custom/models/{modelId}/analyzeresults/{resultId}

Public constructor

https://github.com/Azure/azure-sdk-for-net/blob/e32b2e7f7fab4d7209da788250caa2c145b23c66/sdk/formrecognizer/Azure.AI.FormRecognizer/src/RecognizeCustomFormsOperation.cs#L102-L112

The public constructor, on the other hand, takes a parameter called operationId, which is given by the developer and is expected to be a substring of the aforementioned operationLocation:

{modelId}/analyzeresults/{resultId}

Goals

• Stop using magic numbers and correctly parse the arguments using regex, handling format errors.
• Make sure we support parsing model IDs with characters _, ~, and .. These characters are allowed when naming a custom model.
• Include new tests to verify proper behavior.
• Make sure existing tests still pass reliably.

The following file can be used as a reference: https://github.com/Azure/azure-sdk-for-net/blob/80a63242c93cbbff1ee525248cbd94d89ed72345/sdk/formrecognizer/Azure.AI.FormRecognizer/src/FormField.cs#L90-L91

Related: #10385

[maririos]

By changing the parsing, the errors might change too, so we need to be careful here to not introduce breaking changes. Will wait first on the outcome of https://github.com/Azure/azure-sdk-for-net/issues/17383 before working on this to make sure we have the coverage

[kinelski]

@maririos I wouldn’t say it’s a high-priority issue, since it just changes the behavior internally. @annelo-msft is keeping track of what issues we want closed for P3.