azurerm_cosmosdb_mongo_collection: Fix the issue that expireAfterSeconds property could not be set to -1

[sinbai]

The purpose of this PR:

Currently, there is such a description of default_ttl_seconds in terraform doc, when the value of default_ttl_seconds is set to -1 or 0, it means the collection never expires(The default_ttl_seconds property in Terraform aka the expireAfterSeconds in API). After checking tf code, if default_ttl_seconds <=0 in tf configuration, then terraform will not add "_ts" index and set value of expireAfterSeconds to the value of default_ttl_seconds. Per the doc (TTL behavior for mongoDB collection(container) is the same as SQL, confirmed by service team), it causes the document(item) to never expire despite the ttl of document level being set to a valid value.

In fact, when default_ttl_seconds is set to -1, terraform should set expireAfterSeconds to -1. Also, it is confirmed that 0 is not supported for expireAfterSeconds property. So, the updates are as follows:

• Create a "_ts" index with `expireAfterSeconds` value of -1 when `default_ttl_seconds` is set to -1.
• Update the tf doc to clarify that -1 means never expired.
• Update the validation of `default_ttl_seconds` to allow only a nonzero positive integer, or '-1'.
• Add test case to cover never expires.

Test Results:

PASS: TestAccCosmosDbMongoCollection_serverless (1558.45s)
PASS: TestAccCosmosDbMongoCollection_withIndex (1574.87s)
PASS: TestAccCosmosDbMongoCollection_neverExpires (1580.70s)
PASS: TestAccCosmosDbMongoCollection_basic (1581.52s)
PASS: TestAccCosmosDbMongoCollection_complete (1581.69s)
PASS: TestAccCosmosDbMongoCollection_autoscaleWithoutShareKey (1582.70s)
PASS: TestAccCosmosDbMongoCollection_ver36 (1590.43s)
PASS: TestAccCosmosDbMongoCollection_analyticalStorageTTL (1596.17s)
PASS: TestAccCosmosDbMongoCollection_throughput (1803.67s)
PASS: TestAccCosmosDbMongoCollection_update (1844.47s)
PASS: TestAccCosmosDbMongoCollection_autoscale (1877.26s)

[katbyte]

Thanks @sinbai - LGTM 👍

[github-actions]

This functionality has been released in v3.0.0 of the Terraform Provider. Please see the Terraform documentation on provider versioning or reach out if you need any assistance upgrading.

For further feature requests or bug reports with this functionality, please create a new GitHub issue following the template. Thank you!

[github-actions]

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