public/api-v2/issue/Invoke-JiraGetIssueProperty.ps1

#https://developer.atlassian.com/cloud/jira/platform/rest/v2/#api-rest-api-2-issue-issueIdOrKey-properties-propertyKey-get
function Invoke-JiraGetIssueProperty {
    [CmdletBinding()]
    param (
        # The issue Id or Key
        [Parameter(Mandatory,Position=0,ValueFromPipelineByPropertyName)]
        [Alias("IssueId")]
        [string]
        $IssueIdOrKey,

        # The key name for the property
        [Parameter(Mandatory,Position=1,ValueFromPipelineByPropertyName)]
        [Alias("Keys")]
        [string[]]
        $Key,

        # The JiraContext object to use for the request
        [Parameter()]
        [object]
        $JiraContext
    )
    begin {
        $results = @()
    }
    process {
        $functionPath = "/rest/api/2/issue/$IssueIdOrKey/properties/$Key"
        $verb = "GET"

        $method = New-PACRestMethod $functionPath $verb
        $results += $method.Invoke($JiraContext)
    }
    end {
        $results
    }
}