WebCrypto API has an internal object `supportedAlgorithms`
<https://w3c.github.io/webcrypto/#dfn-supportedAlgorithms> that maps the
all supported algorithms and operations to their desired IDL dictionary
types. It is mainly used by the "normalize an algorithm" algorithm
<https://w3c.github.io/webcrypto/#algorithm-normalization-normalize-an-algorithm>.
We currently implement it as a large `match` block in the
`normalize_algorithm` function.
This patch properly implements the internal object `supportedAlgorithms`
as a new enum type `SupportedAlgorithm`.
By doing so, we can reduce a lot of string comparison to enum matching,
which can be done faster. This patch also separates the dictionary
conversion away from the `match` block to make our code cleaner.
Furthermore, the `exportKey()` method can now utilize the new
`SupportedAlgorithm` to properly check against the algorithm
registration, instead of hard-coding an list of unsupported algorithms
by itself.
Testing: Refactoring. Existing tests suffice.
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Signed-off-by: Kingsley Yung <kingsley@kkoyung.dev>
7342ee0627