feat: implement runtime configuration package with multi-org support (#14624)

runtime configuration package
---------

Signed-off-by: Danny Kopping <danny@coder.com>
Co-authored-by: Danny Kopping <danny@coder.com>

coderd/runtimeconfig/entry.go

@@ -0,0 +1,95 @@
+package runtimeconfig
+
+import (
+	"context"
+	"fmt"
+
+	"golang.org/x/xerrors"
+)
+
+// EntryMarshaller requires all entries to marshal to and from a string.
+// The final store value is a database `text` column.
+// This also is compatible with serpent values.
+type EntryMarshaller interface {
+	fmt.Stringer
+}
+
+type EntryValue interface {
+	EntryMarshaller
+	Set(string) error
+}
+
+// RuntimeEntry are **only** runtime configurable. They are stored in the
+// database, and have no startup value or default value.
+type RuntimeEntry[T EntryValue] struct {
+	n string
+}
+
+// New creates a new T instance with a defined name and value.
+func New[T EntryValue](name string) (out RuntimeEntry[T], err error) {
+	out.n = name
+	if name == "" {
+		return out, ErrNameNotSet
+	}
+
+	return out, nil
+}
+
+// MustNew is like New but panics if an error occurs.
+func MustNew[T EntryValue](name string) RuntimeEntry[T] {
+	out, err := New[T](name)
+	if err != nil {
+		panic(err)
+	}
+	return out
+}
+
+// SetRuntimeValue attempts to update the runtime value of this field in the store via the given Mutator.
+func (e *RuntimeEntry[T]) SetRuntimeValue(ctx context.Context, m Resolver, val T) error {
+	name, err := e.name()
+	if err != nil {
+		return xerrors.Errorf("set runtime: %w", err)
+	}
+
+	return m.UpsertRuntimeConfig(ctx, name, val.String())
+}
+
+// UnsetRuntimeValue removes the runtime value from the store.
+func (e *RuntimeEntry[T]) UnsetRuntimeValue(ctx context.Context, m Resolver) error {
+	name, err := e.name()
+	if err != nil {
+		return xerrors.Errorf("unset runtime: %w", err)
+	}
+
+	return m.DeleteRuntimeConfig(ctx, name)
+}
+
+// Resolve attempts to resolve the runtime value of this field from the store via the given Resolver.
+func (e *RuntimeEntry[T]) Resolve(ctx context.Context, r Resolver) (T, error) {
+	var zero T
+
+	name, err := e.name()
+	if err != nil {
+		return zero, xerrors.Errorf("resolve, name issue: %w", err)
+	}
+
+	val, err := r.GetRuntimeConfig(ctx, name)
+	if err != nil {
+		return zero, xerrors.Errorf("resolve runtime: %w", err)
+	}
+
+	inst := create[T]()
+	if err = inst.Set(val); err != nil {
+		return zero, xerrors.Errorf("instantiate new %T: %w", inst, err)
+	}
+	return inst, nil
+}
+
+// name returns the configured name, or fails with ErrNameNotSet.
+func (e *RuntimeEntry[T]) name() (string, error) {
+	if e.n == "" {
+		return "", ErrNameNotSet
+	}
+
+	return e.n, nil
+}