Add /stats endpoint with 60-second cached total user count

[essiend03-glitch]

closes #82

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[Abdulazeem-code]

Fix checks

[Abdulazeem-code]

could you click the Update branch button on your end, or run git pull origin main locally and push? That will make the tests pass so I can merge this!". Run npm install in stellar-payment-platform directory

[Abdulazeem-code]

Please fix conflict and update branch

[Abdulazeem-code]

Please solve the backend check error. run npm install on the backend folder which is stellar-payment-platform

[Abdulazeem-code]

Please view the details of your backend build error to know what is causing it and resolve it.
Please do this so that i can merge your pr