Add custom keystore support to JWT basic authenticator

[DilshanSenarath]

Purpose

This PR introduces the necessary changes to support configuring a custom keystore for the OAuth protocol. It updates all relevant areas where keystores are used. If a custom keystore is not configured, the system will fall back to the default primary or tenanted keystore.

The main changes include:

• When the KeyStoreManager was previously used to resolve keystore keys, it is now replaced with the IdentityKeyStoreResolver, which dynamically selects the appropriate keystore—custom, primary, or tenanted.

To configure a custom keystore for OAuth, use the following TOML configuration:

[[keystore.custom]]
file_name = "custom.p12"
password = "password"
type = "PKCS12"
alias = "myOrgCert"
key_password = "password"

[keystore.mapping.oauth]
keystore_file_name = "custom.p12"
use_in_all_tenants = true

Related Issue

• Capability to Configure Custom KeyStores for All Inbound Authentication Protocols wso2/product-is#20564

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PR builder started
Link: https://github.com/wso2/product-is/actions/runs/14744666267

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PR builder completed
Link: https://github.com/wso2/product-is/actions/runs/14744666267
Status: success

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Approving the pull request based on the successful pr build https://github.com/wso2/product-is/actions/runs/14744666267