bug(credential): Fix panic in credential Issue

[louisruch]

Vault KV backend returns a nil secret and no error if the secret does not
exist. This caused a panic in during Issue:

panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x20 pc=0x1388279]

goroutine 2639 [running]:
github.com/hashicorp/boundary/internal/credential/vault.(*Repository).Issue(0xc001222200, {0x3b932d0, 0xc001203350}, {0xc000dc6e90, 0xc}, {0xc0010e5e40, 0x0, 0x0})
/home/louis/boundary/internal/credential/vault/repository_credentials.go:67 +0x2d9
github.com/hashicorp/boundary/internal/servers/controller/handlers/targets.Service.AuthorizeSession({{}, 0xc000cd4a38, 0xc000cd4840, 0xc000cd48d0, 0xc000cd4a50, 0xc000cd4870, 0xc000cd4858, 0xc000cd48b8, 0xc0001a8880}, {0x3b932d0, ...}, ...)
/home/louis/boundary/internal/servers/controller/handlers/targets/target_service.go:1059 +0x1525
github.com/hashicorp/boundary/internal/gen/controller/api/services._TargetService_AuthorizeSession_Handler.func1({0x3b932d0, 0xc001203350}, {0x1a0dd40, 0xc000dc8880})
/home/louis/boundary/internal/gen/controller/api/services/target_service_grpc.pb.go:631 +0x78
github.com/hashicorp/boundary/internal/servers/controller.auditResponseInterceptor.func1({0x3b932d0, 0xc001203350}, {0x1a0dd40, 0xc000dc8880}, 0x461279, 0x40d234)
/home/louis/boundary/internal/servers/controller/interceptor.go:262 +0x4e
github.com/grpc-ecosystem/go-grpc-middleware.ChainUnaryServer.func1.1.1({0x3b932d0, 0xc001203350}, {0x1a0dd40, 0xc000dc8880})
/home/louis/go/pkg/mod/github.com/grpc-ecosystem/go-grpc-middleware@v1.3.0/chain.go:25 +0x3a
github.com/hashicorp/boundary/internal/servers/controller.statusCodeInterceptor.func1({0x3b932d0, 0xc001203350}, {0x1a0dd40, 0xc000dc8880}, 0x203000, 0x203000)
/home/louis/boundary/internal/servers/controller/interceptor.go:207 +0x34
github.com/grpc-ecosystem/go-grpc-middleware.ChainUnaryServer.func1.1.1({0x3b932d0, 0xc001203350}, {0x1a0dd40, 0xc000dc8880})
/home/louis/go/pkg/mod/github.com/grpc-ecosystem/go-grpc-middleware@v1.3.0/chain.go:25 +0x3a
github.com/hashicorp/boundary/internal/servers/controller.errorInterceptor.func1({0x3b932d0, 0xc001203350}, {0x1a0dd40, 0xc000dc8880}, 0x18e2b40, 0x0)
/home/louis/boundary/internal/servers/controller/interceptor.go:156 +0x4e
github.com/grpc-ecosystem/go-grpc-middleware.ChainUnaryServer.func1.1.1({0x3b932d0, 0xc001203350}, {0x1a0dd40, 0xc000dc8880})
/home/louis/go/pkg/mod/github.com/grpc-ecosystem/go-grpc-middleware@v1.3.0/chain.go:25 +0x3a
github.com/hashicorp/boundary/internal/servers/controller.auditRequestInterceptor.func1({0x3b932d0, 0xc001203350}, {0x1a0dd40, 0xc000dc8880}, 0x1a1c860, 0xc0010e5280)
/home/louis/boundary/internal/servers/controller/interceptor.go:248 +0x198
github.com/grpc-ecosystem/go-grpc-middleware.ChainUnaryServer.func1.1.1({0x3b932d0, 0xc001203350}, {0x1a0dd40, 0xc000dc8880})
/home/louis/go/pkg/mod/github.com/grpc-ecosystem/go-grpc-middleware@v1.3.0/chain.go:25 +0x3a
github.com/hashicorp/boundary/internal/servers/controller.requestCtxInterceptor.func1({0x3b932d0, 0xc001203260}, {0x1a0dd40, 0xc000dc8880}, 0x18, 0xc0010e52a0)
/home/louis/boundary/internal/servers/controller/interceptor.go:140 +0x5de
github.com/grpc-ecosystem/go-grpc-middleware.ChainUnaryServer.func1.1.1({0x3b932d0, 0xc001203260}, {0x1a0dd40, 0xc000dc8880})
/home/louis/go/pkg/mod/github.com/grpc-ecosystem/go-grpc-middleware@v1.3.0/chain.go:25 +0x3a
github.com/grpc-ecosystem/go-grpc-middleware.ChainUnaryServer.func1({0x3b932d0, 0xc001203260}, {0x1a0dd40, 0xc000dc8880}, 0xc00331abb8, 0x18675e0)
/home/louis/go/pkg/mod/github.com/grpc-ecosystem/go-grpc-middleware@v1.3.0/chain.go:34 +0xbf
github.com/hashicorp/boundary/internal/gen/controller/api/services._TargetService_AuthorizeSession_Handler({0x1ada420, 0xc00093a180}, {0x3b932d0, 0xc001203260}, 0xc001200840, 0xc000465260)
/home/louis/boundary/internal/gen/controller/api/services/target_service_grpc.pb.go:633 +0x138
google.golang.org/grpc.(*Server).processUnaryRPC(0xc000cca540, {0x3bb4c58, 0xc0005a9c80}, 0xc001208480, 0xc0004a7440, 0x499e2b8, 0x0)
/home/louis/go/pkg/mod/google.golang.org/grpc@v1.40.0/server.go:1297 +0xccf
google.golang.org/grpc.(*Server).handleStream(0xc000cca540, {0x3bb4c58, 0xc0005a9c80}, 0xc001208480, 0x0)
/home/louis/go/pkg/mod/google.golang.org/grpc@v1.40.0/server.go:1626 +0xa2a
google.golang.org/grpc.(*Server).serveStreams.func1.2()
/home/louis/go/pkg/mod/google.golang.org/grpc@v1.40.0/server.go:941 +0x98
created by google.golang.org/grpc.(*Server).serveStreams.func1
/home/louis/go/pkg/mod/google.golang.org/grpc@v1.40.0/server.go:939 +0x294

[louisruch]

@talanknight @jimlambrt Pinging you on this as more of an FYI / to have a bigger discussion. This commit has already been approved in a long lived branch but needs to make the 0.7.3 release so pulled it out and into main here. The issue that @jefferai brought up and I wanted to put on your radar was ideally a panic within a request should not panic our controller.

[louisruch]

This commit was already approved when merging into the credential mapping long lived branch. #1790