Update licensing information

Dependencies

• [2] XWHISGCP Extract Amount into separate crate
• [*] YDK6X6PP add a library of important types for beancount
• [*] 2JBFREZG enable additional warnings

Change contents

• edit in beancount/amount/tests/basic.rs at line 1
  [2.40]

  [2.41]
  + // SPDX-FileCopyrightText: 2023 - 2024 Markus Haug (Korrat)

  + //

  + // SPDX-License-Identifier: EUPL-1.2

  +
• edit in beancount/amount/src/lib.rs at line 1
  [4.9836]

  [2.2024]
  + // SPDX-FileCopyrightText: 2023 - 2024 Markus Haug (Korrat)

  + //

  + // SPDX-License-Identifier: EUPL-1.2

  +
• edit in beancount/amount/src/lib.rs at line 7
  [2.2082]

  [5.6396]
  +
• edit in beancount/amount/Cargo.toml at line 1
  [2.1008]

  [2.1009]
  + # SPDX-FileCopyrightText: 2023 - 2024 Markus Haug (Korrat)

  + #

  + # SPDX-License-Identifier: EUPL-1.2

  +