Add documentation on X509 Extensions

use std::fmt;

use nid::Nid;

/// Type-only version of the `Extension` enum.

///

/// See the `Extension` documentation for more information on the different

/// variants.

#[derive(Clone,Hash,PartialEq,Eq)]

pub enum ExtensionType {

	KeyUsage,

	OtherStr(String),

}

/// A X.509 v3 certificate extension.

///

/// Only one extension of each type is allow in a certificate.

/// See RFC 3280 for more information about extensions.

#[derive(Clone)]

pub enum Extension {

	/// The purposes of the key contained in the certificate

	KeyUsage(Vec<KeyUsageOption>),

	/// The extended purposes of the key contained in the certificate

	ExtKeyUsage(Vec<ExtKeyUsageOption>),

	/// Subject Alternative Names

	SubjectAltName(Vec<(AltNameOption,String)>),

	/// Issuer Alternative Names

	IssuerAltName(Vec<(AltNameOption,String)>),

	/// Arbitrary extensions by NID. See `man x509v3_config` for value syntax.

	///

	/// You must not use this to add extensions which this enum can express directly.

	///

    /// ```

    /// use openssl::x509::extension::Extension::*;

	/// use openssl::nid::Nid;

    ///

    /// # let generator = openssl::x509::X509Generator::new();

    /// generator.add_extension(OtherNid(Nid::BasicConstraints,"critical,CA:TRUE".to_owned()));

    /// ```

	OtherNid(Nid,String),

	/// Arbitrary extensions by OID string. See `man ASN1_generate_nconf` for value syntax.

	///

	/// You must not use this to add extensions which this enum can express directly.

	///

    /// ```

    /// use openssl::x509::extension::Extension::*;

    ///

    /// # let generator = openssl::x509::X509Generator::new();

    /// generator.add_extension(OtherStr("2.999.2".to_owned(),"ASN1:UTF8:example value".to_owned()));

    /// ```

	OtherStr(String,String),

}

#[derive(Clone, Copy)]

pub enum AltNameOption {

    /// The value is specified as OID;content. See `man ASN1_generate_nconf` for more information on the content syntax.

	///

    /// ```

    /// use openssl::x509::extension::Extension::*;

    /// use openssl::x509::extension::AltNameOption::Other as OtherName;

    ///

    /// # let generator = openssl::x509::X509Generator::new();

    /// generator.add_extension(SubjectAltName(vec![(OtherName,"2.999.3;ASN1:UTF8:some other name".to_owned())]));

    /// ```

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