Multiplying kets should produce a tensor product

[m93a]

Input code

srepr(qapply(Ket('a') * Ket('b')))

Expected output

TensorProduct(Ket(Symbol('a')), Ket(Symbol('b')))

Actual output

Mul(Ket(Symbol('a')), Ket(Symbol('b')))

Rationale

Qapply converts bra × ket to inner product and ket × bra to outer product. This gives a precedent to also support the rules bra × bra → tensor product of bras, ket × ket → tensor product of kets.

srepr(qapply(Bra('a')*Ket('b')))
> InnerProduct(Bra(Symbol('a')),Ket(Symbol('b')))

srepr(qapply(Ket('a')*Bra('b')))
> OuterProduct(Ket(Symbol('a')),Bra(Symbol('b')))