Consider refactoring Share type

[rootulp]

Context

celestia-app/pkg/shares/shares.go

Lines 11 to 19 in e6bbc30

	// Share contains the raw share data (including namespace ID).
	type Share []byte
	func NewShare(data []byte) (Share, error) {
	if len(data) != appconsts.ShareSize {
	return nil, fmt.Errorf("share data must be %d bytes, got %d", appconsts.ShareSize, len(data))
	}
	return Share(data), nil
	}

Problem

Currently Share is a byte slice. Since the byte slice doesn't guarantee a length, methods like share.NamespaceID() and share.InfoByte() must perform checks on the length of the byte slice prior to returning information. In other words, since the byte slice can't enforce invariants like len(share) == appconsts.ShareSize, all methods that deal with shares must do additional error handling.

Proposal

We may be able to refactor the Share type to be a struct that enforces invariants (e.g. share length). On a related note, we may be able to leverage a builder pattern to encapsulate the logic for constructing shares. Currently a large portion of the share package must operate on byte slices so when we make changes to the share format, several files need to be updated. We could constrain these modifications to a single file (i.e. share.go) if the Share type didn't expose direct byte manipulation to external callers.

[rootulp]

@mojtaba-esk was this closed by #1462?