chore(main): release service 0.4.8

:robot: I have created a release beep boop

policy: add index to fqn column in attribute_fqns table (#1035) (1b0cf38), closes #1053

authz: Return deny on GetDecision if resource attribute lookup returns not found (#962) (7dea640)
core: database clients pooling improvements (#1047) (8193cec)
core: swap out internal issuer for external issuer endpoint (#1027) (c3828d0)
core: update casbin policy to allow authorization service (#1041) (552e970)
policy: provide ns and val fqns back on list attributes response (#1050) (1be04f6), closes #1052
policy: run migrations on db only once for all policy services (#1040) (db4f06f)

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