Update copyright in email templates according to custom text preferences

[UdeshAthukorala]

Proposed changes in this pull request

Recently we have implement an API for the support to customize & localize the text content in end-user facing UIs.
Copyright text can also customize using this new custom text management API and so we need to Update copyright in email templates according to custom text preferences.

Following is a sample custom text prefernce payload.

{
    "type": "ORG",
    "name": "brionmario",
    "locale": "en-US",
    "screen": "common",
    "preference": {
        "text": {
            "copyright": "© {{currentYear}} WSO2 LLC.",
            "site.title": "Asgardeo by WSO2"
        }
    }
}

When applying the copyright text we need to update the current year accordingly.

• ex: © {{currentYear}} WSO2 LLC --> © 2023 WSO2 LLC

Related PR

• Improve custom text api to support both locale code formats like en-US & en_US identity-branding-preference-management#18

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