Post XML request with PEM Key

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I am using Burpsuite to test SSH-public key credentials via an XML POST Request. Essentially I need to send the PEM file text as part of an XML element, like this:\[code\]<PEMKey>-----BEGIN RSA PRIVATE KEY-----MIICXAIBAAK etc...-----END RSA PRIVATE KEY-----</PEMKey>\[/code\]How do I properly format the contents of the PEM file as a string to be submitted as raw XML?