[AI] Server Prompt Templates

[paulb777]

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[andrewheard]

Just a quick thing I noticed: public final class TemplateChatSession: Sendable. This would likely require some refactoring with the history. I'm wondering if we should extract

firebase-ios-sdk/FirebaseAI/Sources/Chat.swift

Lines 29 to 52 in 455d291

	private let historyLock = NSLock()
	private nonisolated(unsafe) var _history: [ModelContent] = []
	/// The previous content from the chat that has been successfully sent and received from the
	/// model. This will be provided to the model for each message sent as context for the discussion.
	public var history: [ModelContent] {
	get {
	historyLock.withLock { _history }
	}
	set {
	historyLock.withLock { _history = newValue }
	}
	}
	private func appendHistory(contentsOf: [ModelContent]) {
	historyLock.withLock {
	_history.append(contentsOf: contentsOf)
	}
	}
	private func appendHistory(_ newElement: ModelContent) {
	historyLock.withLock {
	_history.append(newElement)
	}
	}

into a type and use it for both?

[paulb777]

Done in 004fb94