Remove OnOpampConnectionSettingsAccepted callback (#266)

Contributes to #261

I intentionally left undefined the blocking vs nonblocking
requirement for the callback. I suggest that we refine this
after we make implementations and settle on a particular
behavior.

A continuation of this PR is needed that implements steps 4 and 5
of the flow described here:
#261

client/internal/receivedprocessor.go

@@ -210,9 +210,8 @@ func (r *receivedProcessor) rcvOpampConnectionSettings(ctx context.Context, sett
 
 	if r.hasCapability(protobufs.AgentCapabilities_AgentCapabilities_AcceptsOpAMPConnectionSettings) {
 		err := r.callbacks.OnOpampConnectionSettings(ctx, settings.Opamp)
-		if err == nil {
-			// TODO: verify connection using new settings.
-			r.callbacks.OnOpampConnectionSettingsAccepted(ctx, settings.Opamp)
+		if err != nil {
+			r.logger.Errorf(ctx, "Failed to process OpAMPConnectionSettings: %v", err)
 		}
 	} else {
 		r.logger.Debugf(ctx, "Ignoring Opamp, agent does not have AcceptsOpAMPConnectionSettings capability")

client/types/callbacks.go

@@ -81,15 +81,9 @@ type Callbacks interface {
 	// authorization headers or TLS certificate, potentially also a different
 	// OpAMP destination to work with.
 	//
-	// The Agent should process the offer and return an error if the Agent does not
-	// want to accept the settings (e.g. if the TSL certificate in the settings
-	// cannot be verified).
-	//
-	// If OnOpampConnectionSettings returns nil and then the caller will
-	// attempt to reconnect to the OpAMP Server using the new settings.
-	// If the connection fails the settings will be rejected and an error will
-	// be reported to the Server. If the connection succeeds the new settings
-	// will be used by the client from that moment on.
+	// The Agent should process the offer by reconnecting the client using the new
+	// settings or return an error if the Agent does not want to accept the settings
+	// (e.g. if the TSL certificate in the settings cannot be verified).
 	//
 	// Only one OnOpampConnectionSettings call can be active at any time.
 	// See OnRemoteConfig for the behavior.
@@ -98,12 +92,6 @@ type Callbacks interface {
 		settings *protobufs.OpAMPConnectionSettings,
 	) error
 
-	// OnOpampConnectionSettingsAccepted will be called after the settings are
-	// verified and accepted (OnOpampConnectionSettingsOffer and connection using
-	// new settings succeeds). The Agent should store the settings and use them
-	// in the future. Old connection settings should be forgotten.
-	OnOpampConnectionSettingsAccepted(ctx context.Context, settings *protobufs.OpAMPConnectionSettings)
-
 	// For all methods that accept a context parameter the caller may cancel the
 	// context if processing takes too long. In that case the method should return
 	// as soon as possible with an error.
@@ -137,10 +125,6 @@ type CallbacksStruct struct {
 		ctx context.Context,
 		settings *protobufs.OpAMPConnectionSettings,
 	) error
-	OnOpampConnectionSettingsAcceptedFunc func(
-		ctx context.Context,
-		settings *protobufs.OpAMPConnectionSettings,
-	)
 
 	OnCommandFunc func(ctx context.Context, command *protobufs.ServerToAgentCommand) error
 
@@ -203,13 +187,6 @@ func (c CallbacksStruct) OnOpampConnectionSettings(
 	return nil
 }
 
-// OnOpampConnectionSettingsAccepted implements Callbacks.OnOpampConnectionSettingsAccepted.
-func (c CallbacksStruct) OnOpampConnectionSettingsAccepted(ctx context.Context, settings *protobufs.OpAMPConnectionSettings) {
-	if c.OnOpampConnectionSettingsAcceptedFunc != nil {
-		c.OnOpampConnectionSettingsAcceptedFunc(ctx, settings)
-	}
-}
-
 // OnCommand implements Callbacks.OnCommand.
 func (c CallbacksStruct) OnCommand(ctx context.Context, command *protobufs.ServerToAgentCommand) error {
 	if c.OnCommandFunc != nil {