don't decrypt attachments before tapping + show modal on error

[tomholub]

also mostly fixed #1143. The error was that while the text could be decrypted, the attachments were throwing decrypt errors. I've made it recognize decrypt errors and download the original file, but it needs another issue to actually render the decrypt error before downloading, make sure that's what the user wanted.

Originally posted by @tomholub in #1219 (comment)

[tomholub]

Additionally, there is no need to decrypt all attachments when rendering. Decrypt when tapping attachment.

MessageAttachment should also have an isEncrypted: bool, and we should decide whether to decrypt based on that, when user taps the file.

                // todo - this is decrypting attachments too early
                //   there is no need to decrypt attachments when rendering message,
                //   since user may never tap them.
                //   Instead decrypt them when actually tapped.
                let decrypted = try await core.decryptFile(
                    encrypted: meta.data,
                    keys: keys,
                    msgPwd: nil
                )
                if let decryptSuccess = decrypted.decryptSuccess {
                    attachment = MessageAttachment(
                        name: decryptSuccess.name,
                        data: decryptSuccess.data
                    )
                } else if let decryptErr = decrypted.decryptErr {
                    // todo - once above todo is done and we are decrypting
                    //   at the time of tapping an attachment, render error modal
                    // if user confirms the modal, they can download the original msg
                    // then can remove the warning
                    logger.logWarning("attachment could not be decrypted due to error: \(decryptErr.error.type) - \(decryptErr.error.message)")
                    attachment = MessageAttachment(
                        name: meta.name,
                        data: meta.data
                    )
                } else {
                    throw AppErr.unexpected("decryptFile: expected one of decryptErr, decryptSuccess to be present")
                }

[tomholub]

Since we're adding isEncrypted to each attachment, we could also surface that in UI / list of attachments, with encrypted (green) or not encrypted (red) badge for each attachment?

[tomholub]

This will also need an appium test for the above message. Tapping the message should produce a modal:

Error decrypting attachment: \(decryptErr.error.type) - \(decryptErr.error.message)

This will likely download a corrupted file. Download anyway?

[yes] [no]

Taping yes downloads the original (encrypted) file. Tapping no will hide the modal.