BasicAuthenticationInterceptor causes ClassNotFoundException when spring-security-config is absent (client-only starter)

[bkmuraliext]

Bug Report
Summary
BasicAuthenticationInterceptor in spring-grpc-core imports GrpcSecurity, which extends AbstractConfiguredSecurityBuilder from spring-security-config. When using spring-grpc-client-spring-boot-starter (client-only), spring-security-config is not on the classpath, causing a ClassNotFoundException at runtime on every gRPC call.

Version
spring-grpc: 1.0.3 / Spring Boot: 4.0.6

Steps to Reproduce
Use spring-grpc-client-spring-boot-starter:1.0.3 (not the full spring-grpc-spring-boot-starter)
Configure BasicAuthenticationInterceptor as a @GlobalClientInterceptor
Make any outbound gRPC call

Actual Behaviour
java.lang.NoClassDefFoundError: org/springframework/security/config/annotation/AbstractConfiguredSecurityBuilder
at BasicAuthenticationInterceptor$1.start(BasicAuthenticationInterceptor.java:53)
Caused by: java.lang.ClassNotFoundException: ...AbstractConfiguredSecurityBuilder

Root Cause
BasicAuthenticationInterceptor uses GrpcSecurity.AUTHORIZATION_KEY. GrpcSecurity is a server-side class extending AbstractConfiguredSecurityBuilder from spring-security-config. Loading the interceptor's anonymous class triggers loading of GrpcSecurity, which fails without spring-security-config on the classpath.

Suggested Fix
Move AUTHORIZATION_KEY out of GrpcSecurity into a shared constants class with no Spring Security dependencies, or define it inline in BasicAuthenticationInterceptor:

private static final Metadata.Key AUTHORIZATION_KEY =
Metadata.Key.of("Authorization", Metadata.ASCII_STRING_MARSHALLER);

[therepanic]

Thanks for the report, @bkmuraliext. That is a really good catch! I have submitted a PR to fix it: #410. Feel free to take a look.