add customer encryption key for upload and download blob request

[Leavrth]

support x-ms-encryption-algorithm, x-ms-encryption-key and x-ms-encryption-key-sha256 for upload/download blobs in headers.

[demoray]

Can you discuss this choice, instead of using

Suggested change

	if let Some(cpk_info) = &this.encryption_key {
	headers.add_ref(cpk_info);
	}
	headers.add(this.encryption_key);

This is made possible by the following:

azure-sdk-for-rust/sdk/core/src/headers/mod.rs

Lines 25 to 27 in be63d1e

	impl<T> AsHeaders for Option<T>
	where
	T: Header,

[Leavrth]

Thank you for your review.

The struct CPKInfo contains 3 headers: EncryptionKey, EncryptionKeySha256 and EncryptionAlgorithm. That's because once the EncryptionKey is specified, the other 2 headers must be provided. (from azure-sdk-for-go)

The this.encryption_key is wrapped by Option, for which I find there has been an implement:

// ./sdk/core/src/headers/mod.rs:L25
impl<T> AsHeaders for Option<T>
where
    T: Header,
{
    type Iter = std::option::IntoIter<(HeaderName, HeaderValue)>;

    fn as_headers(&self) -> Self::Iter {
        match self {
            Some(h) => h.as_headers(),
            None => None.into_iter(),
        }
    }
}

The T has a trait bound Header, which has the function name and value. But the trait Header can not be implemented by CPKInfo. So I cannot directly use headers.add(this.encryption_key);.

[Leavrth]

@demoray PTAL

[Leavrth]

Maybe we can just specify the AsHeaders::Iter to expand the scope. See the code as followes:

impl<T> AsHeaders for Option<T>
where
    T: AsHeaders<Iter = std::option::IntoIter<(HeaderName, HeaderValue)>>,
{
    type Iter = T::Iter;

    fn as_headers(&self) -> Self::Iter {
        match self {
            Some(h) => h.as_headers(),
            None => None.into_iter(),
        }
    }
}

[Leavrth]

@demoray @heaths PTAL

[Leavrth]

In the commit c18fbdd, I modify the std::option::IntoIter<(HeaderName, HeaderValue)> to std::vec::IntoIter<(HeaderName, HeaderValue)> so that we can integrate multiple headers into one type.