docs: create feature request for context support and link throughout

Create GitHub issue #264 for multi-tenant context support with detailed
requirements, acceptance criteria, use cases, and implementation hints.
Link to the issue from README known differences, OpenAPI spec /contexts
endpoint, and auto-generated API reference. Add Multi-Tenant Contexts
and Schema Linking rows to the feature comparison table.

Author: millerjp

README.md

@@ -85,6 +85,8 @@ Unlike Confluent Schema Registry, which uses Kafka itself (a special `_schemas`
 | **Prometheus Metrics** | ✅ | ✅ | ✅ | ✅ |
 | **REST Proxy** | ❌ | Separate | Separate | ✅ |
 | **Schema Validation** | ✅ | ✅ | ✅ | ✅ |
+| **Multi-Tenant Contexts** | [Planned](https://github.com/axonops/axonops-schema-registry/issues/264) | ✅ | ✅ | ✅ |
+| **Schema Linking** | ❌ | ❌ | ✅ | ❌ |
 | **Single Binary** | ✅ | ❌ | ❌ | ❌ |
 | **Memory Footprint** | ~50MB | ~500MB+ | ~500MB+ | ~200MB+ |
 
@@ -206,7 +208,7 @@ AxonOps Schema Registry implements the Confluent Schema Registry REST API v1:
 
 **Known differences:**
 
-- **Contexts** -- In Confluent Schema Registry, contexts are a multi-tenancy feature that allows multiple schemas with the same subject names and IDs to coexist in separate namespaces (e.g. `".team-a"`, `".team-b"`). Subjects are qualified with a context prefix (e.g. `:.mycontext:my-subject`), and schema IDs are unique within each context. This is primarily used for Schema Linking and enterprise multi-tenant deployments. AxonOps Schema Registry operates as a single-tenant registry -- the `GET /contexts` endpoint always returns `["."]` (the default context only), and context-qualified subject names are not supported.
+- **Contexts** -- In Confluent Schema Registry, contexts are a multi-tenancy feature that allows multiple schemas with the same subject names and IDs to coexist in separate namespaces (e.g. `".team-a"`, `".team-b"`). Subjects are qualified with a context prefix (e.g. `:.mycontext:my-subject`), and schema IDs are unique within each context. This is primarily used for Schema Linking and enterprise multi-tenant deployments. AxonOps Schema Registry operates as a single-tenant registry -- the `GET /contexts` endpoint always returns `["."]` (the default context only), and context-qualified subject names are not supported. See [#264](https://github.com/axonops/axonops-schema-registry/issues/264) for the feature request to add context support.
 - **Cluster coordination** -- Confluent uses Kafka's group protocol for leader election between registry instances. AxonOps instances are fully stateless with no leader election -- database-level constraints (transactions, LWTs) handle coordination instead.
 
 ---

api/openapi.yaml

@@ -1647,7 +1647,9 @@ paths:
 
         AxonOps Schema Registry operates as a single-tenant registry. This endpoint
         always returns `["."]` (the default context only). Context-qualified subject
-        names are not supported.
+        names are not supported. See
+        [#264](https://github.com/axonops/axonops-schema-registry/issues/264) for the
+        feature request to add context support.
       operationId: getContexts
       tags:
         - Metadata

docs/api-reference.md

@@ -3744,7 +3744,7 @@ Returns the list of contexts defined in the registry.
 
 In Confluent Schema Registry, **contexts** are a multi-tenancy feature that allows multiple schemas with the same subject names and IDs to coexist in separate namespaces (e.g. `.team-a`, `.team-b`). Subjects are qualified with a context prefix (e.g. `:.mycontext:my-subject`), and schema IDs are unique within each context. This is primarily used for Schema Linking and enterprise multi-tenant deployments.
 
-AxonOps Schema Registry operates as a single-tenant registry. This endpoint always returns `["."]` (the default context only). Context-qualified subject names are not supported.
+AxonOps Schema Registry operates as a single-tenant registry. This endpoint always returns `["."]` (the default context only). Context-qualified subject names are not supported. See [#264](https://github.com/axonops/axonops-schema-registry/issues/264) for the feature request to add context support.
 
 > Example responses