Fixes #490 - Add support for Namecheap

[eloekset]

An implemenation for Namecheap.

I've deployed and used it for three of my own domains now and it works fine.

Since I can't send PRs for the wiki, this is the documentation that should be added about configuration of the Namecheap provider:

Namecheap

App settings

• Acmebot:Namecheap:ApiKey
  • Your Namecheap username (not an email address)
• Acmebot:Namecheap:ApiKey
  • API Key on your Namecheap Profile -> Tools -> API Access page

Example API Token configuration

Navigate to https://ap.www.namecheap.com/settings/tools/apiaccess/

Client IP addresses must be whitelisted in your Namecheap account to be able to call the API. For Azure Function apps, this is a bit tricky, because you don't know which IP address the function app uses until it has tried and got rejected.

To find the IP address, you'll have to look at the Application Insights Performance view and look for logs on GetZones. There you should find an entry for api.namecheap.com GET /xml.response and the Path contains the ClientIp=nn.nnn.nn.nnn parameter showing the IP address that was used.

You have to go to your Namecheap profile page and whitelist this IP address.

But there's no guarantee that the function app uses the same IP address when it renews the certificates some months later.

[eloekset]

Link to Issue #490