Add support for garde crate as alternative to validator

[jirutka]

Can you please consider adding support for garde as an alternative to validator? It’s better designed than validator. The reasons for starting a new project are mentioned in Keats/validator#201.

[Wicpar]

+1 this request, validator does not support enums.
In the mean time validator can be replaced, structs will just have duplicate attrs with #[garde] and #[validate]

[GREsau]

This seems doable. Looking through the current garde attributes, I think we can respect most of them:

• #[garde(required)] - same as validate(required)
• #[garde(ascii)] - use regex pattern ^[\x00-\x7f]*$ (or ^\p{ASCII}*$, but that is less-widely supported)
• #[garde(alphanumeric)] - use regex pattern ^[\p{Alpha}\p{N}]*$?
• #[garde(email)] - same as validate(email) (set "format": "email")
• #[garde(url)] - same as validate(url) (set "format": "uri")
• #[garde(ip)] - set "format": "ip" (not a standard JSON Schema format, but is consistent with the JsonSchema impl for IpAddr)
• #[garde(ipv4)] - set "format": "ipv4"
• #[garde(ipv6)] - set "format": "ipv6"
• #[garde(length(<mode>, min=<usize>, max=<usize>, equal=<usize>)] - similar to validate(length(...)), but with the extra "mode". How to handle that?
• #[garde(range(min=<expr>, max=<expr>, equal=<expr>))] - similar to validate(range(...)), but also supports "equal" (why?)
• #[garde(contains(<string>))] - similar to validate(contains = ...)
• #[garde(pattern("<regex>"))] - similar to schemars(regex(pattern = ...)) (not supported by validator)
• #[garde(pattern(<matcher>))] - similar to validate(regex(path = ...))
• #[garde(prefix(<string>))] - similar to "contains", we can just prefix the pattern with ^
• #[garde(suffix(<string>))] - similar to "contains", we can just suffix the pattern with $
• #[garde(credit_card)] - ignore
• #[garde(phone_number)] - ignore (schemars currently supports validate(phone) but this was removed from the validator crate - probably remove from schemars too?)
• #[garde(matches(<field>))] - ignore
• #[garde(dive)] - ignore
• #[garde(skip)] - ignore
• #[garde(custom(<function or closure>))] - ignore
• #[garde(inner(...))] - same as schemars(inner) (not supported by validator)

[GREsau]

This is now implemented in schemars 1.0.0-alpha.14

Most, but not all, of the attributes I listed above are now supported - see the updated docs for a full list: https://graham.cool/schemars/deriving/attributes/#supported-validatorgarde-attributes