Add OVH Provider

[bhubert]

I added OVH which is a cloud / DNS / domain provider really popular in France and at least Europe.

The code is complex because their api is complicated to call with a signature to generate based on the content of the call that needs to be added in header on each requests

[bhubert]

hi @shibayan ! do you think you will accept this PR or is OVH to small in your opinion to make it a great addition to your project ?

[shibayan]

Overall, the structure and format of the code should be consistent with other provider implementations. Consistency with other provider implementations must be maintained.

e.g. https://github.com/shibayan/keyvault-acmebot/blob/master/KeyVault.Acmebot/Providers/GoDaddyProvider.cs

[bhubert]

Overall, the structure and format of the code should be consistent with other provider implementations. Consistency with other provider implementations must be maintained.

e.g. https://github.com/shibayan/keyvault-acmebot/blob/master/KeyVault.Acmebot/Providers/GoDaddyProvider.cs

I reordered and rewrote some part of the code to make it looks like GoDaddy provider as much as possible. You were right it's much better like this, thanks !

[bhubert]

Overall, the structure and format of the code should be consistent with other provider implementations. Consistency with other provider implementations must be maintained.
e.g. https://github.com/shibayan/keyvault-acmebot/blob/master/KeyVault.Acmebot/Providers/GoDaddyProvider.cs

I reordered and rewrote some part of the code to make it looks like GoDaddy provider as much as possible. You were right it's much better like this, thanks !

@shibayan it's been a while and i forgot about this PR, could you check if the last version was ok ? thanks !