Add pagination support for show/list spire-server CLI commands that use List APIs

[rturner3]

When using the spire-server CLI to fetch data via SPIRE Server APIs with commands like entry show or agent list, if the amount of data returned by the SPIRE Server APIs exceeds the gRPC default max response size of 4 MB, the entire command fails to execute.

For larger scale environments, this greatly reduces the usefulness of these CLI commands, since many times the command fails due to too much data being returned by the Server. It would be very helpful in such cases if these CLI commands used pagination in their Server API requests so that the data can actually be presented to the user, since the Server APIs are implemented with gRPC and are not otherwise easy to invoke without writing a custom application.

[sachinkumarsingh092]

@rturner3 aren't we already paginating the response from the server API and then using the same for listings?

[rturner3]

In order for the server to use pagination, the client needs to set the page_size field to a value > 0 for each request, and for all but the first request, the client needs to set the page_token field to the value of next_page_token from the previous response. The CLI commands are not setting page_size or page_token in the API request messages today.

See ListAgents and ListEntries handlers for reference.

[sachinkumarsingh092]

@rturner3 what would be a good page_size and page_token value to be set here? I think this should fix the pagination for the above two references (ListAgents and ListEntries).

[rturner3]

The page size should depend on the approximated maximum size of each entity represented as a serialized protobuf message.

Taking ListAgentsResponse as one example, we need to consider the maximum number of bytes it may take to represent an Agent, and the maximum size of a page token (size of a UUID represented as a string).

The page token in the request message is directly copied from the previous response message, e.g. for ListAgents: https://github.com/spiffe/spire-api-sdk/blob/7ff3eb0759ce242a38fd02aa368b3d7a33ac7316/proto/spire/api/server/agent/v1/agent.proto#L103

[rturner3]

The entry show command was never updated to use pagination. Re-opening this issue until that is completed.